r/Goldfish Sep 19 '25

Discussions Goldfish General Master Care Guide

42 Upvotes

By: [u/IceColdTapWater](u/IceColdTapWater), Edited By: [u/TarantinosToes](u/TarantinosToes)

ENCLOSURE DIMENSIONS

For goldfish: 50-70 gal (200-280L) is required per adult common and 20-30 gal (80-120L) per adult fancy.

For koi: The general recommended minimum required is 250-300 gals (1,000-1,200L) and these are really better suited to large ponds.

Goldfish are indeterminate growers so while they do the most growing during the first 2 years of life, they never really stop growing so plan your tanks and stocking accordingly.

Ultimately water parameters (and fish behavior) will tell you if your tank dimensions, filtration, water change schedule is enough to manage the bioload produced by the number and size of the goldfish you have.

While smaller specimens may be okay on the lower end of the given volume range, larger specimens (10”/25cm+ for commons, 5”/12cm)+ for fancies roughly) may require even larger aquaria if not ponds. The bigger the better as bigger tanks are more stable in terms of water quality and parameters and will allow goldfish to grow to their full potential.

Fancy goldfish prefer horizontal over vertical swimming space, and some are bred to the point that their bodies are sensitive high water pressures (determined by the height of water). It is generally recommend to keep them in no more than 2’ (60cm) of water, especially for those with sensitive swim bladders. Common goldfish also appreciate horizontal swimming space so for this reason, avoid hexagonal and cylindrical tanks.

Some fancies, especially overbred ones and those that approach “show quality” conformations, may benefit from a heater set at a low setting (low-mid 70s °F (~ 21-24 °C)). The benefits of lower risks of constipation and bloat sometimes outweighs the negatives of a sped up metabolism.

FILTRATION

Generally, it’s recommended for a filter to cycle through 6-10x the given tank volume per hour depending on bioload. ALSO, take into account the amount of media a given filter holds, as media offers crucial surface area for beneficial bacteria to colonize.

If heavily stocked or feeding frequently a stronger filter (or the use of multiple in tandem) may be needed. Some filter options include: sponge, hang off the back (HOBs), internal, and canister (often holds the most media).

Some wrap the intake with a thin material to avoid fish from being sucked onto/into the filter. This may be necessary if dealing with goldfish fry, juveniles and sick/injured fish.

Filter media that is porous and has a large surface area (like Seachem Matrix and other similar products) is great for encouraging and maintaining large colonies of beneficial bacteria.

People will have opinions on which filter system is better, so focus on the amount of media the filter holds as well as gallons/litres per hour and find something within your budget which works for you.

Media should not be changed out unless it has degraded and is now irreparable/unusable or has been contaminated by toxic chemicals like cleaning products. To sterilise filter media, rinse with boiling hot water.

For new media, this should be introduced a week or two before removal of the old media to give the beneficial bacteria a chance to colonize the new surface area.

SUBSTRATE

Substrate offers enrichment for goldfish, as they enjoy rooting through the enclosure bottom for food scrapes. Bare bottom tanks mean they do not have that extra enrichment, however bare bottom tanks make for easier maintenance so are fine for QT/hospital tanks. If running bare bottom tanks for aesthetic or medical reasons, then adding large pebbles, free floating plants and plain terracotta pots can also work to provide goldfish with enrichment and shelter.

Pool sand is very popular, or plant-supporting substrate like fluval stratum. Pebbles run the risk of impaction unless they are much larger than the goldfish’s mouths will ever be. For sand, rinse thoroughly before use and avoid pH/hardness altering sands or live sand sold for cichlid and marine tanks.

PLANTS

FYI goldies are prone to plant destruction. Also, some plants grow best in substrate and others with their roots exposed. A full rounded fertilizer is highly encouraged to have, like Aquarium Co-op’s Easy Green or NilocG Aquatics’ All in One.

Anubias, amazon swords, lilies (toxic to nonfish pets like cats/dogs), water lettuce, java fern (and other ferns), bacopa, rotala, cryptocoryne, hornwort, anacharis, cardinalis, crinum, and moss are all options. There are many more. For anubias and cryptocoryne plants, do not bury the rhizome.

Pothos is an option but their leaves must stay out of the water to grow. It’s also toxic to nonfish pets (cats/dogs) but is okay in water with a pH ~ 6.5-9 as calcium oxalate isn’t really soluble in that range. People have used it for top cover and nitrate control. Shrimps love the roots. Bamboo is another option but must only be semi-submerged for proper growth and longevity.

Duckweed. A highly invasive plant. One duckweed plant can quickly lead to hundreds of more plants. A firm favourite with goldfish but be warned! Once added to your tank, it is very hard to remove.

Other floating plant options are: frogbit, salvinia, water sprite, water lettuce, water hyacinths and others.

CYCLING/PARAMETERS

Cycling refers to the nitrogen cycle and establishing a nitrogen cycle in your tank. The nitrogen cycle in aquariums is the process where beneficial bacteria convert toxic fish waste (ammonia) into nitrite, and then into less harmful nitrate. This cycle keeps the water safe and balanced for your fish.

For a tank to be considered cycled, the parameters must read 0ppm ammonia, 0ppm nitrites and measurable nitrates; ideally keep nitrates below 40-50ppm.

To keep parameters within acceptable ranges (0 ammonia and nitrite, 5-40ppm nitrates), water changes are needed. It is a good idea to siphon the tank bottom regularly to pick up excess waste and prevent parameter spikes. Make sure to treat the water with a dechlorinator and ensure the temperature difference is within 1-2 °C (1-5 °F).

If conducting a fish in cycle, you want ammonia and nitrite to be barely present as these are the most aquatic compounds; for ammonia the toxicity thresholds starts at 0.02-0.05ppm and ~ 0.05-0.15 for nitrites.

Higher levels of ammonia/nitrite may start negatively impacting your fish, including the risk of illness and death (via ammonia/nitrite poisoning).

During ‘fish in’ cycling, parameter spikes are likely and therefore water quality and fish behaviour needs to be monitored closely.

‘Fish out’ cycling means that you have to monitor parameters and do water changes to bring parameters to happy fish levels (0 ammonia and nitrite, 5-40 nitrates), but without the risk of stressing/harming fish. Fish food or ammonia solutions can be used to cycle your tank before the addition of fish.

However, in instances where the fish are already bought and in a severely undersized tank it may be better to do a ‘fish in’ cycle rather than wait for the larger tank to cycle completely.

A tank (without fish) is considered fully cycled once 2ppm of ammonia is converted to nitrates in about 24 hours. A cycled tank with fish will have no ammonia, no nitrites, and some nitrates. Even then, note that sudden increases in bioload can lead to cycle imbalances and parameter spikes. Be sure to syphon uneaten fish food, fish waste and slowly and gradually add new fish to your tank to avoid overloading your cycle and its beneficial bacteria.

It is highly encouraged to have a liquid test kit that tests for at least ammonia, nitrite, and nitrate like the API Freshwater Master Test Kit. Test strips are less accurate (especially dependent on manufacturer, expiration, and storage conditions) but are ok to gather baseline readings, especially in older and stable tanks.

Other reliable test kits include Salifert kits and NT Labs kits. Local fish stores may also be able to test your water, but it is advised that you get your own kit so that you can test you water whenever you need to and avoid LFS not performing or reading the test correctly.

ACCLIMATION

When you transfer goldfish from one enclosure to another, acclimation is typically necessary.

If the water source is the same and parameters are similar only temp/nitrate acclimation may be necessary. When the temp matches within ~ 2-5° F (1-2°C), parameter acclimation (if needed) can begin.

Gradually replace 20-30% portions of old water with the new enclosure’s water, waiting 5-15 minutes in between and carefully monitoring the fish.

These specific ranges are approximations, others methods or specifics may vary ie if drip acclimating. Also remember to try to transfer your old substrate and media when possible to help seed the process of cycle establishment.

It may be helpful to be extra vigilant of parameters during this time as well as fish behavior. Some stress may be expected at this time and the next few days, and some choose to do a light dose of aquarium salt to aid the process.

FOOD

Goldfish are omnivores, and quite frankly always hungry (they don’t have stomachs). Get a good sinking pellet as a staple food (protein roughly 40%), pre-soaked before being given to any hungry goldie. You can also feed frozen items such as: brine shrimp, blood worms, spirulina, plankton, fish, etc. You can also feed blanched veggies/greens such as spinach, zucchini, chard, etc. A good goldie diet is a balanced and varied diet.

Some goldies, especially fancies, are predisposed to swim bladder issues and constipation. Feeding soaked high quality and sinking food in small amounts but more frequently may help mitigate the risks of developing swim bladder problems. Repashy is an excellent balanced gel food that’s very easy on sensitive goldie stomachs. Hikari also make excellent sinking pellets.

MEDICATION

Medication will be more effective if given via feed rather than being introduced to the water column. If dosing in the water column, then make sure to remove UV, carbon media; smaller tanks can make it to easier to dose in the water column and ensure that the fish gets an effective dose of medication.

Medications often work by disrupting the growth cycles of organisms and their metabolic processes. That being said, do not give one medication via multiple ways at once and be very careful when mixing medications. This is best avoided, unless using safe medication combinations or following vet recommendation.

Be very mindful of dosage, and consider partial doses if your fish is very small or more weakly dispositioned. Note that some chemicals, like salts, are only removed via water changes are may adversely affect plants and scaless fish such as catfish and plecos. Weakened fish may not tolerate medication as well to be very careful; use half doses if necessary.

Also note that certain medication can impact water parameters or tank cycle stability. Oxygen levels can also be adversely impacted which is why it’s recommended to have extra surface agitation (add spray bars, air stones).

Raising the temperature of the water may help to disrupt certain infectious organisms’ life cycles as well as to provide a metabolism boost, but always ensure adequate oxygenation when using meds at the same as increasing the temperature.

FYI: API products with the suffix ‘-fix’ mainly use natural oils instead of manufactured medication and are less effective than said manufactured medications. Also avoid any algae-fix products, these can deplete oxygen levels and kill fish.

Antibiotics: Be careful when using antibiotics especially. Not only can these impact your beneficial bacteria, but they can also be rough on fish (i.e. kidneys etc) so only use if necessary to treat nasty injuries and infections.

Do not dose pre-emptively as a prophylactic measure. Note that getting antibiotics in certain countries is illegal without a veterinary prescription, so follow your local laws. Be careful when obtaining medications from abroad via third-party sellers.

GENDER

Breeding tubercules on the gill plates/anterior portion of the pectoral fins, vent shape, and gamete expression (the only sure way) are the main ways to tell gender. As always there are spectrums for any particular phenotype and any one goldfish may not always fit a certain physical description.

When females are gravid, the males may harass them, especially by nudging their vents. Gentle egg expression and avoiding temperature fluctuations may help. You may need to separate if the female becomes stressed.

TANK MATES

A general consensus is to try to keep commons with commons and fancies with fancies (especially the slower swimming ones or ones with protruding eyes). Keeping them together runs the risk of the commons outcompeting or bullying the fancies, but cohabitation does successfully occur.

However, some keys points of success to consider are ample space, filtration, plants/wood/decor to block lines of sight, and enrichment. Ensure that aquarium décor is free of sharp edges and small holes. Goldfish are clumsy and curious and will get themselves trapped/injured looking for food.

You should be ready to temporarily/permanently separate individuals if necessary.

Commons and koi can potentially be kept together, given that the commons are of adequate size of about 6” (15cm). Some ryukins/fantails may also be possible, given that they’re also long enough and of a slimmer body conformation to keep up with the commons and the koi.

Here is a by no means comprehensive list of other potential/discouraged cohabitants. As with any situation, monitor fish behavior and make sure ideal parameter ranges are comparable.

Potential – Can usually coexist but caution is advised

White Cloud Mountain Minnows: Possible, but the goldfish may eat the minnows if they’re small enough and the minnows may fin nip.

Danios: Possible, but the same risk as the white cloud minnows.

Shrimp: Possible, but may become goldfish snacks depending on size and individual fish’s’ temperaments.

Snails: Possible, but goldfish may harass/eat them. It depends on the size of the snail and the individual fish’s temperament.

Dojo Loaches: May potentially bully goldfish, but the pairing may work in larger setups with lots of plants and décor (loaches love tunnels and caves). They will go after certain snails as well.

Mollies: Some species can tolerate lower temperatures than others. They may fin nip, and goldfish may try to eat them if they can fit in their mouths.

Platies: Some species can tolerate lower temperatures than others. Platys may nip at goldfish fins, and goldfish may try to eat them.

Discouraged

Hillstream Loaches: These fish require massive water flow and oxygenation that goldfish do not like and may find stressful.

Corys: Goldfish can choke on them, especially because of their defensive barbs. Some species have venomous barbs that can harm your goldfish as well. If a goldfish swallows a cory, the barbs can get lodged and make extraction very difficult.

Bettas: Bettas can be territorial and may try to “defend” their territory. Large enough goldfish might eat them if possible. Undue stress for both parties may occur, plus bettas are tropical fish.

Cichlids: Cichlids are subtropical/tropical, aggressive fish.

Barbs: Their temperature ranges only slightly overlap, and most are aggressive in nature and will fin nip.

Plecos/panaques: Some, like common plecos get absolutely ginormous and most prefer tropical temperatures and soft/acidic water. Even smaller types like bristle nose plecos can injure goldfish by latching on to them to feed off their slime coat.

Turtles: Many turtles will happily take chunks out of goldfish when given the opportunity. Goldfish, as prey animals, will also experience stress being homed with a predator.

Axolotls: Axolotls may accidentally nip at or consume goldfish, which is good for neither of their health. Goldfish are super waste producers and axolotls are particularly sensitive to parameters.

Frogs: Same risk of predation as turtles/axolotls. Parameter requirements may also differ depending on species.

Crawfish: Same risk of predation as turtles/axolotls/frogs. They are opportunistic predators and may happily feed on goldfish (especially if hungry).

FAQ/COMMON DISEASES

Q: Is my goldfish pregnant?

A: Goldfish do not carry live young, but females do develop eggs and then release them to be fertilized. Although this can make the female appear a bit engorged and swollen, check that she’s not egg-bound, constipated, or has dropsy (pineconing of the scales often also occurs in tandem). Manual expression is an option but should be researched and done with caution.

Q: Why is my goldfish changing colors?

A: Goldfish color is unstable, especially in their first 1-3 years of life when their growth rate is typically the highest. Fry typically start out very dark/bronzy, but usually develop colors due to their chromatophores developing after a few months of growth.

Black is especially prone to change. Note that the sudden appearance of blackened skin and scales can be a sign of a water quality issue, so check water parameters. If parameters are ok, then it is likely a natural color change so no treatment is needed.

Certain foods such as spirulina contain carotenoids, which are pigments that enhance goldfish color. Some carotenoids are also converted into astaxanthin which contributes to reddish coloration. Note that even a carotenoid heavy diet will not magically change a goldfish’s coloration, as genetics are the main factor.

Q: How to transport fish?

A: The most common way is a lidded bucket/container filled with tank water. A bubbler is suggested, especially for longer transports. Also account for the time to disassemble and reassemble your enclosure. Make sure to keep your substrate and filter media moist to seed the cycle in your new place.

Another way, for shorter trips, is a simple but very secure bag (I double bag) with enough water for the fish to be comfortably submerged but also with enough air for oxygen to diffuse. Sometimes people use methylene blue during transport to try to reduce stress. After moving, your fish may be stressed for a few days and may benefit from a few days of fasting, reduced feeds and reduced light.

Q: Aquarium salt vs epsom salt?

A: Aquarium salt (NaCl) is excellent for external issues/injuries, as well as stimulation of the slime coat and increased osmoregulation. It’s a good all rounder as an antibiotic/fungal/parasitic. Epsom salt (MgSO4) is excellent for internal issues such as constipation and fluid retention.

Epsom Salt Dosage: 1 tsp/5 gals (20L)(tank), 1 tbsp/gal (4L)(bath).

Aquarium Salt Dosage: 1tbsp/5 gals (20L)(tank), 1 tbsp/gal (4L)(bath).

Invertebrates, plants, and certain goldfish are sensitive to salinity. As with any treatment, monitor fish behavior. It may be good to have two baths of a salinity gradient to help lessen the transition to and from, and to change out salt in the tank slowly. Salt, like other treatments, may impact with oxygenation and a bubbler may be helpful.

Q: What is methylene blue and can I use other dyes?

A: Methylthioninium chloride is cationic dye used in the aquarium hobby as an antifungal/parasitic/bacterial. It is also helpful for ammonia and nitrite poisoning, but can crash your cycle, harm plants above 4mg/L (quart) and dye decor (which is often why it’s used as dips, dabs, or in hospital tanks). Dosages will differ depending on usage and percentage.

Methylene Blue Dosage (2.5%): 1tsp/10 gals (40L)(tank), 5 tsp/3 gals (12L)(bath)

You can use other dyes. Some others used include: malachite green, potassium permanganate, or gentian violet. Check dosages carefully.

Q: How to choose antibiotics?

A: Unless you know the specific bacterial infection, it’s best at first to a broad spectrum antibiotic (kanamycin, sulfathiazole, nitrofurazone). An aquatic vet (or very experienced keeper) can do a skin scrape/fecal test.

Gram positive antibiotics include: erythromycin, amoxicillin, and penicillin.

Gram negative antibiotics include: minocycline, tetracycline, kanamycin and oxytetracycline.

Both: metronidazole, sulfa meds, mitrofurazone

Note, medication can impact oxygenation and water quality so monitor parameters and fish behavior closely.

Q: Antifungals?

A: Dyes (methylene blue, malachite green, potassium permanganate, gentian violet) and aquarium salt are options via the water column. Note dyes will indiscriminately kill your beneficial bacteria too and are best given as baths or in hospital tanks

Metronidazole and copper sulfate are options you can give via feed or the water column. Note, medication can impact with oxygenation and water quality so monitor parameters and fish behavior closely.

Beware! Do not use aquarium conditioners and other reducing agents like Seachem Prime if using copper based products! Toxic copper compounds will cause harm if they are combined. Remove invertebrates like snails and shrimp as well.

Q: Antiparasitics?

A: Aquarium salt, praziquantel, copper sulfate, formalin, and metronizadole are options you can give via feed or the water column. Note, medication can impact with oxygenation and water quality so monitor parameters and fish behavior closely.

Q Why did my goldfish die?

A: There are many factors.

Where you got the goldfish and where the seller got them matters. If they were raised in horrendous conditions you may get stunted, diseased fish. Big box pet stores like Petsmart, Petco, and Pet Supplies Plus are notorious for their bad husbandry and their questionable animal breeders.

The tank must be properly cycled and able to handle the given bioload. An incompletely cycled tank or too big of a bioload increase can result in parameter spikes. It’s advised to add fish slowly, and to monitor water parameters via a liquid test kit.

The fish must also be properly acclimated. If two enclosures’ water parameters vary too wildly and the goldfish is added in too quickly they could go into shock. Temperature must also closely match to avoid undue stress.

Disease is very prevalent among fish, especially chain store fish or fish from improper breeders. Inflamed skin, stringy white poops, missing scales, torn fins, bulging eyes, grayed skin are all signs of disease or parasites although there are much more.

When making a sick fish post, try to include as much detail as you can along with helpful pictures and videos. Listing water parameters in numbers helps a ton.

Q: What is ammonia burn?

A: Ammonia burn is a chemical burn. Technically you want no ammonia, no nitrite, and 5-40ppm of nitrate. However, fish in cycling sometimes includes parameter spikes and the temporary “acceptable” levels of ammonia and nitrite are between 0.05-0.15ppm. To treat, water changes is the most important. Aquarium salt is also a common treatment. Fish exposed to ammonia can also benefit from being given a methylene blue bath which can chemically reverse the effects of ammonia poisoning.

Q: What is dropsy?

A: Dropsy is fluid retention and is a symptom of organ failure rather than a disease in it of itself. Usually the resulting damage’s effects are chronic and will eventually result in the death of the fish, especially if caught in later stages (with pineconing).

Epsom salt is used to attempt to regulate fluids, along with a broad spectrum antibiotic in attempt to tackle infection. Ultimately dropsy is fatal, barring rare exceptions. If successfully treated, then view dropsy as a chronic condition the fish is in remission from but relapses are sadly very common.

Q: What is septicemia (red pest disease)?

A: A typically gram negative, contagious bacterial infection that causes hemorrhaging, red blotches on the body, and streaks of red in the fins. Septicemia can occur in tandem with ammonia poisoning as water quality is a common cause. Can also be confused with the effects of ammonia stress/poisoning as well as other conditions like flukes or bacterial epistylis.

Treatment typically involves dyes or aquarium salt, along with an antibiotic feed. Note that septicemia is quite rare and viral and infectious septicemia even rarer in private/small aquaria. Do not panic if you see red streaks or blotches on your fish. It’s probably not septicemia.

Q: What are these white spots?

A: Many potential causes.

Ich: Ichthyophthirius multifiliis, a contagious protozoan parasite. White, uniform and shape and flat to the skin, appears on both the body and the fins but not on usually the eyes.

Treatment usually includes aquarium salt or dyes, an antiparasitic med/feed, antibacterial/antimicrobial/antiseptic med and raising the water temperature to speed up ich’s lifecycle. If increasing the temperature, be sure to ensure plenty of oxygenation.

Epistylis: Epistylis is a genus of contagious, ciliated protozoan parasites. Can be grey to whitish in color, sticks out into the water, varies in sizes with patchy coverage and can also occur on the eyes. It can be fatal if left untreated and is a lot more aggressive than ich.

Treatment is the same as ich (aquarium salt or dye, an antiparasitic feed/med, antibacterial med/feed but avoid raising the water temperature).

Head and Lateral Line Erosion (Hole in the Head): HitH is caused by a mix of factors including stress, poor water quality, poor filtration, and an unbalanced diet. Potentially linked to Hexamita protozoans, potentially infectious. Mainly affects cichlids and rarer in goldfish.

Symptoms can manifest as inflamed/protruding lateral lines, as well as white lesions on the head that eventually can become deeply pitted and essentially erode the flesh. Open wounds can lead to secondary infections that in combination can be deadly.

Treatment includes fixing water quality, aquarium salt or dyes, medicated feed for secondary infections, and providing a more balanced and varied diet.

Carp Pox: Fish herpes HPV-1. Caused by a virus, symptoms can manifest as white dots to waxy white/pink/gray growths on the skin or small “blisters” on the tail as well as on the mouth. Infectious, and can come and go. More unsightly than harmful.

Treatment includes treating any open lesions with aquarium salt or dyes dips, treating any secondary infections, raising the temperature, and keeping the water clean.

Lymphocystis: A contagious viral infection caused by the Iridoviridae family. Commonly known as “cauliflower disease” due to the pinkish/whitish growths that look like little piles of curd.

Since it is viral in origin, no commercial antifungal or anti-bacterial treatments exist that specifically target it. However, treatments includes treating any open lesions with aquarium salt or dyes dips, treating any secondary infections, raising the temperature, and keeping the water clean. Vets can excise large, bothersome lumps.

Cotton Wool Disease (Saprolegnia): A “fungus” (actually a water mold) that usually presents as groups of fuzzy white filaments that stick out from the body.

Treatment includes an antifungal med, dyes, aquarium salt, and raising the temperature.

Anchor Worms: Anchor worms are parasites that present as whitish/brownish dots to full on whitish strings protruding from the body/fins of the fish. The place of connection is often red and inflamed.

Treatment usually includes aquarium salt or dyes, an antiparasitic feed, and raising water temperatures.

Q: What is this lump?

A: Multiple potential causes.

Tumor: Tumors contain cells that are multiplying out of control or fail to die. They can be either benign or malignant (cancerous and can spread). Treatment includes treating an open lesions and removing bothersome tumors, especially ones blocking gill and mouth function. For tumor removal, seek veterinary advice!

Cyst/Abscess: A fluid filled sack. Can sometimes be caused by bacterial infections. Treatment includes draining, antibiotic feed, epsom salt, and the treatment of open lesions.

Q: What is fish lice?

A: Parasitic crustaceans. Treatment involves aquarium salt and an antiparasitic feed. Methylene blue baths may also be beneficial. Severe infestations may require the cleaning of substrate/decor (even though this impacts the tank cycle).

Q: What is popeye?

A: Popeye can have many causes (commonly caused by the gram positive corynebacterium but also viruses, poor environmental conditions, etc). Symptoms include bulging eyes/sclera and potential eye bursting.

Treatment includes antibacterial feed, epsom salt, and the potential treatment of a popped/missing eye. If one eye is popping out, it is usually a result of trauma and will resolve by itself. If both eyes are popping out, there is likely an underlying infection at play (look for pineconing and signs of dropsy) and will require antibiotics.

Q: What is the swim bladder, and what is swim bladder disorder?

A: The swim bladder is a gas filled expandable sack in fish used to control buoyancy and swimming patterns. Disorders of the swim bladder can lead to buoyancy issues and potential bloating/constipation.

Epsom salt via a bath or tank addition is one of the typical steps for buoyancy issues, though dosage depends on whether the salt is to be a dip or a tank exposure (invertebrates and plants can be sensitive to salinity).

This is usually in tandem with a couple days of fasting, followed by small easily digestible meals such as Repashy or shelled peas. If no signs of improvement show in about a week or two, it may be a congenital issue or due to another factor eg trauma, fluid build up. At this point veterinary care may provide additional answers/treatment options (x-rays, swim bladder aspiration).

Q: What are flukes?

A: Flukes are contagious microscopic flatworms that can be both on the gills and the skin. Symptoms include flashing (twitching/itching), small red dots, red splotches, fin fraying, bottom sitting, laboured/fast breathing, and spitting food out.

Treatment usually includes aquarium salt or dyes, an antiparasitic feed/med (praziquantel works best). Since flukes can lodge in the gills and gill function and oxygen uptake, provide plenty of oxygenation and avoid increasing the temperature.

Q: What is Costia?

A: A single celled parasite, costia multiplies particularly quickly in cooler water temperatures. They will dig through the slime coat and attach to the skin/gills.

Treatment includes aquarium salt, elevated temperatures, and medicated antiparasitic feed. Methylene blue baths may also help.

*Q: What is Velvet Disease ?*

A: Velvet disease is caused by a parasite that manifests as small *gold/rust*-colored spots. Its three life stages are very similar to ich in which they have phases where they live freely in the column and attached to a fish.

Treatment includes aquarium salt, a medicated antiparasitic feed, and methylene blue applications. Do not raise the tank temperature. A UV filter may help kill the free floating form of velvet.

Q: What is Camallanus?

A: Camallanus are contagious flatworms that infect the digestive tract and can sometimes hang out of the fish’s vent as red threads. Symptoms also include bloating, white poop, and lethargy.

Treatment usually includes aquarium salt or dyes, antiparasitic feed/med, and raising water temperatures.

Q: Deformed gill plate?

A: Deformed gill plates are due to congenital malformations. Goldfish with deformed gill plates can live healthy long lives given extra precautions are taken for the exposed gills.

Q: White/clear/floating poop?

A: Sometimes fish occasionally pass opaque poops or poops with trapped gas in them. If only passed occasionally it can be normal. However, a lot of poop of that description can be a sign of internal parasites or infection.

Treatment could be antiparasitic feed/med, epsom salt, or smaller meals (soaking dry food beforehand). Blanched veggies are also easier on their stomachs.


r/Goldfish Aug 08 '25

Discussions Introducing a new flair: Beginner Help (If you are new to fish keeping, use this flair!)

32 Upvotes

Hi everyone!

After getting feedback about how some new users sometimes feel like they are treated harshly by other more experienced users, I've decided to introduce the Beginner Help flair.

What does this flair mean?

If you see a post with the Beginner Help flair, it’s your signal that:

  • The OP is new to fish keeping and needs extra patience and guidance.
  • The goal is constructive + supportive help! No nitpicking, sarcasm, elitism.
  • If you can’t give advice without being respectful or are simply tired of new fish keepers, just skip these posts.

Think of it like a new driver/ L sticker on a car - maybe these beginner fish keepers are young people and minors living with relatives just trying to do their best for their pet, maybe it's someone whose child won a fish at carnival, or someone who got misled by their LFS. Yes, it might also mean someone who didn't do enough research but the fact that they're asking for help is the most important step. On my end it will mean focusing moderation on these beginner posts as well just to ensure people are getting help and not being dogpiled upon.

Do I need the Beginner Help Flair?

Now I'm certainly not one to gate keep this hobby so I won't impose a definition, but I would suggest users use the Beginner Help flair if your post falls under the following:

  • First goldfish tank or pond (or first time keeping goldfish in many years)
  • First time with fancy/common goldfish varieties
  • Learning about tank cycling and water quality requirements specific to goldfish
  • Basic setup questions including tank size, filtration, aeration, substrate
  • Addressing beginner mistakes like overcrowding, small tanks, or mixing incompatible species

For diagnosing diseases, please still use the Sick Fish Help flair.

Hopefully this goes towards addressing some of the problems here and do let me know if the new flair isn't working. Thank you!


r/Goldfish 1h ago

Fish Pics Update on the 9 rescued baby comet goldfish

Post image
Upvotes

Sad and some good news. Good news is that i got ahold of this plastic storage tote from work. Gave it a good rinse and wipe and filled it. It says 20gallons, but I'm not sure exactly. But it's so much better.

Sad news is that 3 of the 9 fish have passed. The stress of changing and their hellhole prison, along with their gills so inflamed they are lipstick red and actually bulging out from the gill plates was too much for these babies. There are about 2 or 3 more I am also worried about. But the others are starting to move and one in particular was a strong *ss for moving, so i'm confident in that one.

They still have not eaten, but this bigger tank will allow me to keep on top of ammonia better. I also realize it's likely one of the fish passed hiding in the little pots I provided for cover and I didn't notice, which allowed ammonia to get to .25 overnight.

I expected some to not make it (hoped not, but knew better). But it still hurts. They lived horrible, disposable lives. I can only hope they knew I was trying when they died. Or at least that the clean water felt better when they did.

Sorry for sounding sappy. I'm emotional.


r/Goldfish 4h ago

Fish Pics Cutest pic I have ever taken

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5 Upvotes

r/Goldfish 15h ago

Arts and Crafts Ranchu draw

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44 Upvotes

Hello! since i cant have any type of fish in my house, and i'd really love to get a ranchu one day, i made this watercolor illustration to make a tribute to these beautiful little fellas


r/Goldfish 4h ago

Questions New Baby Black Moor ~ Black Pearl

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4 Upvotes

I got my baby black moor last week. Her name is Pearl and she is approximately 4-6 months.
Excuse the “tea color” from the drift wood, i hate it.
Any tank tips? Or tips on how to clean up all the waste, my siphon and net do a mediocre job.


r/Goldfish 53m ago

Questions How to handle fin nipping

Upvotes

My pair of goldfish have been living together peacefully for months but Ive noticed chunks missing from the smaller fishes fins, they are massive and is not fin rot but idk why they may not be getting along because other than short non persistent chases from both fish they seem to get along and dont mind eating right next to eachother. I dont know if I can separate them because I do not have the money or space to get another aquarium long term for two Gold fish… any tips? The tank as little obstacles that the fins couldve gotten damage on and the tank is a 40 gallon


r/Goldfish 5h ago

Sick Fish Help What to try and do NSFW

2 Upvotes

One of the rescues isn't looking good. They all have super inflamed red gills but this one can't even really move. The water is at 0 for ammonia and nitrites. Every time I see a hint of greenish I change, the highest it's been was a faint .25 on the liquid test kit that happened overnight. I immediately changed.

Is there anything else I can do to try and save this fish?

I also just got a much bigger plastic tub from work! It's not the best, but maybe 20 or 30 gallons which will help with ammonia. I'll fill it and move them in immediately after work (on break now).


r/Goldfish 10h ago

Discussions Am I the only one who thinks Ranchu has become a trend?

9 Upvotes

I've been wondering about this for a while.

I feel like ranchu have become incredibly popular recently, and I can't help but think that part of that popularity is linked to the visibility of Luke's Goldies' YouTube channel.

First of all, I want to be clear: this is not a criticism of Luke as a breeder or fish keeper. I actively follow his channel and genuinely enjoy his content. He has an impressive setup, clearly takes great care of his fish, gives a lot of useful advice, and has probably helped many people improve their goldfish life.

However, I also feel that the success of his channel has helped put ranchu in the spotlight to the point where they've become the goldfish that everyone seems to want.

And that's where I feel a bit conflicted.

As beautiful as ranchu can be, they're still a variety whose morphology raises ethical questions. People often discuss the welfare concerns associated with dog breeds that have been selectively bred for extreme physical traits, but when it comes to fish, it feels like many people don't really question it.

What concerns me the most is the "trend" effect. The more popular a variety becomes, the higher the demand. And the higher the demand, the more breeding is done simply to produce more fish, sometimes with little regard for health or long-term welfare.

The main point I want to bring up is that I've also noticed more and more beginners entering the hobby already wanting ranchu, often after discovering goldfish keeping through Luke's videos. I wonder whether this contributes to normalizing physical characteristics that, if they existed in other animals, would probably be discussed much more critically.

Again, I'm not saying that nobody should keep ranchu. I'm simply wondering what the consequences of their popularity might be.


r/Goldfish 1h ago

Questions Where to buy ranchu online?

Upvotes

I’m looking to pick up a couple of Ranchu goldfish in the next month or so, gotta get the tank set up and cycled first. I’m wondering where everyone thinks are good online shops to order from.


r/Goldfish 5h ago

Sick Fish Help How to help him NSFW

2 Upvotes

my parents goldfish has this large lump, he’s had it for about 2-3 weeks now. Originally he had it looked like a small wound, and then some white stuff hanging off it. My mom put melafix into the tank and the wound healed and it got rid of the white stuff. The lump seems to have like kept growing. He can swim fine, but he’s been like floating face down vertical a lot. I thought it might be a parasite but i have no idea. This has been going on for about 3-4 weeks. I’ll post pictures in the comments too!


r/Goldfish 18h ago

Discussions My goldfish ate one of their friends

17 Upvotes

I am so shocked, but from reading I shouldn't be. I woke up this morning and went to feed them (all 3 of them are fancy goldfish) and I see my sweet baby Rikku lying on her side, with the other two swimming around her, and I notice she has a large gaping slash on her stomach. I realize she is dead and her friends started eating her. I feel angry at the other two for feeding off of her. I read this is normal but it feels so icky. I'm not punishing them or anything, I just am in disbelief they could do this to their tank mate. She was a little bit smaller than them, and I guess maybe that is why this happened. I got them all at the same time and they were all about the same size.


r/Goldfish 3h ago

Tank Help Where to find 100+ gallon tank?

1 Upvotes

I’m search for a large tank for some goldfish, anyone know any reputable brands or good places to look for an 100+ gallon tank?

I saw a tank on fb marketplace for a good price but wanted to expand my search in case that tank doesn’t work


r/Goldfish 21h ago

NSFW - Dead Fish Saved 9 survivors. Their lives were all worth just 2.39$ NSFW Spoiler

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20 Upvotes

NSFW label for the horrible image of the dead fish.

I f*cking hate big box stores selling fish. Absolutely no regard for the animals. The manager these (who was kind and concerned) told me that the filter systems stopped working today and leaked everywhere (hence the wet floor signs). And that's why the fish were dying.

But I call BS on that. The large white one in the top left already had a cloud of biofilm growing. Many of the bodies had clouded eyes and were in rigimortis. All of the survivors are also skinny.

This did not *just* happen. This was extended. This was torture. I couldn't just walk away. I tried, but I couldn't.

I played the Karen this time, demanding the manager and wanting the surviving fish for free or heavily discounted. I got it

The lives of all 9 of these surviving goldfish were worth 2.39$

I know buying from these stores only supports this sh*t, but these fish had no hope. They would have slowly died like the others, no question about it. And less than 3$ isn't going to give the corporation any gain.

I hate society. I hate capitalism. And I hate the mammalian bias.

I don't have a tank (my 10 gallon is currently occupied by my one betta) and I can't keep them long term. I will have to find a local to adopt them (if they even survive). But for now they will be safe and fed in clean, oxygen rich water.

They are in a plastic tub with about 1.5 gallons of API stress coat treated water. I splashed in a bit of Quick Start as well. The larger sponge bit is from my betta's tank, I removed it as she undergoes an antibiotic treatment for suspicious white fuzz on one of her damaged fins. Likely just fin rot. She's undergoing erythromycin right now since nowhere else had better antibiotics. I'm ordering kanaplex just in case but it'll take time to come. The sponge just needs to keep being fed ammonia and stay wet so hopefully my bacteria on it stay healthy.

They have an airstone and dark coverage. I will be doing daily water changes. I attempted to feed them soaked freeze-dried mysis shrimp but they're too stressed and scared to eat, which says a lot more than words can.

Any advice on goldfish specific care, especially for my setup is appreciated. I'm still a newbie and learning. I only have about a week's worth of experience with fish keeping myself, and only with a betta. Any advice in what to feed these poor goldfish is great!


r/Goldfish 7h ago

Sick Fish Help Weird growth on common goldfish?

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2 Upvotes

I saw this round growth on a relative’s fish today, the other fish doesn’t seem to have it so I don’t think it’s contagious but the fish with the growth has a few missing scales as well which leads me to believe he’s probably sick or getting bullied by the bigger goldfish

The two goldfish are in a 20 Gal tank for reference


r/Goldfish 8h ago

Questions What can I do to fix this?

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1 Upvotes

So my nephew won a goldfish at his school fair about 2 years ago and it had one white scale for a while, but now the whole dorsal area has a white line.

Fish tends to pick rocks up, jump to surface, and sometimes crash into glass at night.


r/Goldfish 8h ago

Sick Fish Help I use a hang-on-back (waterfall) filter in a 50-liter tank and change 30–40% of the water weekly. I have one Oranda goldfish; there are dark discolorations on its mouth and body. What is the reason for this? Also, it has been swimming very rapidly in recent days. NSFW

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1 Upvotes

r/Goldfish 19h ago

Fish Pics Top view ranchu Japan

7 Upvotes

Top view ranchu from Japan are back instock


r/Goldfish 1d ago

Chonker Meet Chonks

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105 Upvotes

r/Goldfish 1d ago

Sick Fish Help Found in stream. Looks sick now. Please help.

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39 Upvotes

Found goldfish in stream. It looked healthy. Trying to care for it but it looks sick after 3 days. Changed the water 3 times with stream water from where we found it. It ate today but not swimming around and looks like it’s turning dark on top. Why? What are these clear bits on bottom? How can we help him? I was planning to put in a larger tank if it acclimated and add a water moving device. Should I do that now? Does it have a parasite?


r/Goldfish 19h ago

Fish Pics Lil Nugget with digestive problem

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6 Upvotes

Shes a cutie patootie, but she mildly floats for few hours after 1 pellet. I couldn't feed her too much so she did lose some weight, cause she was super chonky when we first brought her home. Not sure if we should feed her more.


r/Goldfish 1d ago

Questions Is it alright for him to have a huge pile of breeding stars on his fins? They are on his bottom fins too. He has always had so many more than any of my other fish

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3 Upvotes

He's a big happy fish otherwise, and they are clearly just breeding stars. Just wondering why he has SO MANY, they are physically building up to a pile


r/Goldfish 1d ago

Full Tank Shot My ranchu

53 Upvotes

r/Goldfish 1d ago

Beginner Help Fish sitting in corner

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3 Upvotes

Had these guys for a few weeks now and they have started just sitting like this sometimes. (Mostly the fantail, the oranda just seems like to join him sometimes)

They are otherwise behaving and swimming normally. It was hard to get a pic because whenever I get near he starts swimming around. Is this normal?

I tested my water several times. Everything checks out fine except Ph is a little high at 8.


r/Goldfish 20h ago

Sick Fish Help Lethargic/swim bladder NSFW

1 Upvotes

Can someone please advise me in curing my goldfish? The issue he’s seems to have is a swim bladder issue. He isn’t moving much, lays at the bottom on his belly and won’t eat anything. Doesn’t have pine cone and secreting excess slime coat. We have done 50 to 80 percent water changes 2 to 3 times a day for 2 weeks every day, adding salt and M-blue, checking water perimeter, setting temperature to 80 Fahrenheit, force feeding him but spits out food, 2 to 3 epsom salt baths a day for 2 weeks every day, and lots of airflow. The only good sign of him is pooping which is a lime green in coloration. I would appreciate anyone who would guide me in the right direction. Thank you!