Can A Goldfish Live In A 5 Gallon Tank?

Fish add a soothing and tranquil ambiance to any space, be it a home, office, or recreational center. Plenty of fish can be inexpensive to buy, including certain breeds of goldfish. But the price of tanks can be eyewatering. How much space does a goldfish really need? After all, in the 80s, people won them at carnivals from tiny bowls. Can a goldfish live in a 5-gallon tank? 

Goldfish should not be kept in a 5-gallon tank. Goldfish should have at least a 20-gallon tank. Many goldfish would do well in a 100-gallon tank. Goldfish have a lot of bio-waste, and a larger tank keeps them healthy. Even if the goldfish doesn’t die in a small tank, its growth will be stunted. 

One of the most common and inexpensive goldish are comets. If treated well and appropriately homed, they reach 12 inches (30.5 cm), with some overachievers getting as big as 14 inches (35.5 cm). So even if you bring home this cute tiny goldfish, it isn’t meant to stay that size. It is young and, like any other living creature, needs space to grow. 

Feeding Goldfish | Photo 56242840 © Kanokrut Tesakarn |

Do Goldfish Really Need A 20-Gallon Tank? 

No, sometimes goldfish need a 100-gallon tank or a full-on pond, especially if you have more than one. (Some goldfish can live very happily with your koi.) But if you are going to keep a goldfish, you need a 20-gallon tank at a minimum.

Yes, if your child comes home from school with some poor wee goldfish in a plastic bag, you can keep it in a small temporary home until your Amazon order arrives. But your free goldfish varieties tend to be on the bigger side, so you might want to get at least a 40 to 50-gallon, especially if you might add a friend. 

There are also some smaller breeds of goldfish that only get up to around 6 inches, and they might be fine in a 20-Gallon tank. Although your average fancy breed needs a 30-gallon tank. 

Fancy goldfish are more expensive, so rarely given away for free. So when you buy one, get the exact info on it, as fancy goldfish do not do well in a tank that is too small or too big. They, like Goldilocks, need their tanks just right. 

Why Do Goldfish Need So Much Space? 

Goldfish need more space due to their bulk. So yes, there are fish that might be the same length as your goldfish that can happily live in a smaller tank. But goldfish have bellies that are both long and wide. They’re like the Shetland ponies of the fresh-water sea.

And like a pony, goldfish take big dumps, more politely referred to as “bio-waste.” Goldfish’s bio-waste contains nasty things that are not good for their gills or brains. There are friendly bacteria you can buy to help keep the bio-waste from poisoning your fish between water changes. But bacteria can’t fix it alone. The waste needs to be diluted, hence the bigger tanks. 

How Long Will A Goldfish Live? 

Goldfish can live up to thirty years, with an average lifespan of 10-15. Many people don’t want to bother buying an adequately sized tank for their goldfish because they assume goldfish have short lives. Thus, they see the expense of a large tank as a waste of money. But the reason goldfish die early is they are improperly cared for, and this includes small tanks.

When a goldfish is stunted by being kept in a too-small tank, this creates problems with its internal organs. Squished internal organs reduce a goldfish’s lifespan. The goldfish is also more likely to become ill due to the amount of waste in the bowl relative to its size. This further reduces the goldfish’s lifespan.

But a goldfish that is fed properly and allowed to grow up in a nice roomy tank will easily live for over a decade if not three. 

How Do I Know If My Goldfish Is Healthy?

Goldfish can’t tell you they are happy, so here are a few signs to look out for when assessing the health and happiness of your goldfish. 

Signs Of A Happy Goldfish

  • Happy goldfish keep busy and active. They don’t tend to hide behind objects or plants unless something is wrong. 
  • It swims up to eat immediately at feeding time. (Shetland ponies-of-the-fresh-water-sea, remember? They like to eat.) 
  • Its body is in good condition: no white spots, torn fins, or weird blemishes, and its eyes are not bulging more than normal. Scales should be their usual vibrancy.
  • Gills are expanding at a regular rhythm, neither faster nor slower than usual. 

Environment Check List For Goldfish

To maintain your goldfish’s happiness, there are a few things to keep in mind. 

  • Make sure it is in a large tank, at least 20-gallons, ideally between 40 to 100. 
  • Ensure the water has a pH of 7-7.4 and its temperature is between 62 – 72 F (16.6-22.2 C).
  • Make sure the tank has plants and ornaments, even if fake. Happy goldfish are active goldfish, and they need small joys to keep them that way. That said, while researchers did discover that goldfish can tell the difference between Bach and Stravinsky, the fish prefer quiet. 
  • Make sure you have an air stone. This will help keep your water’s oxygen level’s correct. 
  • Make sure you have a filtration system. 
  • Make sure it has a friend. Goldfish are social. It doesn’t have to be another goldfish. Plecos or Cory cats can not only be a friend but will help keep the tank cleaner. 
  • Make sure you are changing your tank’s water. It’s advised that new tanks have 10 percent of their water changed per week. If the tank is established and you’ve got that good bacteria doing its job, 25 percent once a month should suffice. 

Signs Of An Ill Goldfish

Fish can look off for several reasons. Some signs point to needing to fix something in its tank. Others are a sign of illness, and you should quarantine the ill fish from the rest and treat it. Here are a few tank-related problems and a few common ailments. 

Inflamed gills that are moving faster than normal.
Your tank’s water is poor.Check the pH, cleanliness and that the pump and filters are working.

You probably need to change the water, too.
Fast gill movement while “gulping” at the surface.
Your tank’s oxygen levels are poorMake sure the filter is on and the air stone. You also need to change the water. 
Wisps of “hair” have developed on your fish, and it isn’t eating well. 
Tank’s water has mold, and the water needs to be treated. 
Red spots on fish. Fish keeps rubbing against the tank walls and objects in the tank. Fish liceThis usually happens when a new fish wasn’t properly quarantined, so now all the fish have lice.

Common treatments to add to the water are Dimilin or Trichlorfon. 
Your fish’s fins are looking torn, streaked, or ragged. 
Fin RotCheck the water quality and isolate the ill fish from the rest.

You will probably need to treat the ill fish with antibiotics.
Your fish has developed white freckles and is scraping its body against surfaces.
IchThis usually happens when water from a new fish is added to the tank.

The tank’s water now needs to be treated. Common solutions are copper sulfate, Acriflavine, Malachite Green, or Formalin.