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How Many Goldfish Can I Put in a 3 Gallon Tank? (Answered)

Goldfishes are excellent starters for beginner aquarists. They are pretty to look at and also easiest to maintain. With proper care and maintenance, goldfishes can live up to eight to ten years. But they’re also quite sensitive about their environment and space.

How many goldfish can I put in a 3-gallon tank?

According to the rule of one inch of fish per gallon, you can put three one-inch fish in a 3-gallon tank. But it would be a very small tank for them to breathe and happily live, as they grow very rapidly. You may use a 3-gallon tank at the beginning but will need a bigger tank soon.

Fish tanks come in various sizes from 2.5 gallons to 210 gallons. To put goldfish in the fish tank, you must be careful to choose the size of the gallons. The bigger the gallon tank, the better. The reason is, goldfish grow very rapidly. 

They have a maximum growth of six inches and can be two feet long depending on the type.

The rule of thumb is one inch of fish is suitable per gallon. According to the rule, for a gallon tank, you can keep three one-inch goldfishes. Because one-inch goldfish requires at least one square foot of the surface area of the fish tank.

But you’ll need to change the water regularly to keep your goldfish alive.

Moreover, it also depends on the species of fish you’re putting in and the number of items you’re adding like rocks, decorative plants, filters, stones. Because that’s how you are reducing the amount of water and they may not breathe and move easily.

However, it’s better to use a little bigger fish tank than 3 gallons to keep your fish happy. You can use 3 gallons for the baby goldfishes but as they grow bigger they won’t fit in this little tank. For an adult fancy goldfish, a minimum 10 gallons fish tank is required. 

So, you have to consider a bigger tank in the future for the goldfishes or they may pass young.

Can goldfish survive in a small tank? What happens if you put goldfish in a small tank?

For a small tank, goldfishes are not a good choice. Though it might not be a problem if they are baby goldfishes, they’ll need a larger tank soon when they grow a little bigger. They need places to hide, to have fun and move easily, and also to breathe properly. 

They will be stressed and affected by various diseases.

If you are thinking of a feeder goldfish, then it might be a good choice for a 10-gallon tank or less than that. But for fancy adult goldfish choosing larger than 10 gallons would be great. But if you put goldfish in a small tank they’ll mourn from:  

Shortness of breath:

Because of the small tank, goldfish don’t find enough space to swim and move when they grow bigger. They feel suffocated in the tank and face shortness of breath.

Ammonia poisoning:

Goldfish excrete large amounts of ammonia so, if the tank is very small, it begins to build up in the tank and affects all the goldfishes. Ammonia burns the skin, damages fins, and scales and it’s one of the common assassins of goldfish.

GIH is produced:

GIH is a growth-inhibiting hormone. The hormone is produced in the goldfishes on the water if the tank is very little and the water is dirty which hampers the growth of the goldfish.

Is a 3-gallon tank big enough for a goldfish?

A 3 gallon tank is too small for a goldfish. A feeder goldfish or a baby goldfish, not more than 2 inches might survive in a 3-gallon tank but as soon as it grows bigger, it’ll need a bigger tank to survive.

The growth of the goldfish will be hampered in this small size of tank and it won’t be able to move and breathe properly. Moreover, fish waste, ammonia, and pollution build up quickly in this small tank and as a result, the fish will face various diseases.

How long can a goldfish live in a 3-gallon tank?

Goldfish can live more than ten years if they get proper care and enough space. In a small tank like 3 gallons, a goldfish can live six months to two years depending on its species, growth, and proper care. 

But if they get very poor care as well not enough space to swim, they may live two to a maximum of six months.

Can comet goldfish live in a 3-gallon tank?

Comet goldfish won’t survive in such a small fish tank. They actually need more space than the normal fancy goldfish. Comet goldfish need a minimum of 20 gallons of space to live even when they are pretty small. 

40 to 50 gallons would be a good choice or if possible 75 gallons tank would be perfect for an adult comet goldfish to live happily.

Can you put 2 goldfish in a 3-gallon tank?

You can put 1-inch 2 goldfish in a 3-gallon tank or even can three, according to the one-inch per gallon rule. But it would not be the right decision to keep two goldfishes in such a small tank. 

You’ll need to change the tank when they will grow bigger to keep your goldfishes healthy and alive.

How big a tank do you need for goldfish?

Goldfish need larger space to swim freely for their health and wellbeing. They grow very quickly and their average length is 6”-8”. They can even go 2 feet long depending on their species. So, you must have to choose tanks according to their species and length.

For one or two feeders or fancy baby goldfish 10 gallons will be a good decision but for a comet needs a minimum of 20 gallons. For an adult, a fancy goldfish minimum of 20 gallons will be good but 30 gallons will be perfect for both fancy and comet

If you want to add more goldfishes just add 10 gallons extra for each.

What fish are good for a 3-gallon tank?

Your options are quite limited as your tanks only have 3 gallons. Actually, 3 gallons tank isn’t good enough for an adult fish to live happily but a baby and quite smaller fish can be a good choice. You can choose:


Tetras are small fishes that can live happily in a 3-gallon tank. Bloodfins, serapes, and red eyes tetras would be great choices to put three to five tetras together in a 3-gallon tank.


Bettas are colorful, long-finned fishes and perfect for small tanks. Delta, double tail, veil bettas can live quite well in a 3 gallons tank with a filter and a heater.


Guppies grow not more than two inches so, it would be a good choice for your 3 gallons tank. But for 3 gallons, one or a maximum of two guppies would be okay.


Killifish are the world’s smallest fish that are found in freshwater and you can put killifish in a 3 gallons tank without any hesitation. But any more than one won’t be suitable for 3 gallons tank.


Glofish can be put in 3 gallons tank temporarily but they’ll need a larger tank when they’ll grow up. They’re very easy to care for fish.

Final thoughts

3 gallons will be too small to keep any goldfish. Following the rule of “one-inch goldfish per gallon,” you might put three one-inch goldfish in it but temporarily. As they’ll grow they will require more spaces to move and live properly and you’ll have to change the tank soon.