Two Goldfish In A Tank: Did You Know Which Is The Ideal Size For Their Health?

When you decide to get aquarium fish as pets, choosing a comfortable tank is always the first step, goldfish is beyond that. In fact, the tank size is the most important because two goldfish in a tank will grow up so fast day by day. What will happen if they don’t have enough space? Let’s think deeper. Our goldfish won’t get the proper territory, which leads them to be aggressive, stressed, and many other hidden risks such as diseases. You know that common goldfish can grow up to 10 inches in length, while fancy goldfish usually grow up to 8 inches. Living in this condition surely can’t make them happy and healthy, that’s why they never live a full of their lifespan.

The question is, when you have two goldfish in a tank, which size is the best choice?

Calculator The Amount Of Goldfish For Each Liter

Two goldfish in a tank

The fact that a normal common goldfish requires at least 30 gallons of tank space, which is approximately 120 liters. Therefore, you can have one goldfish for every 120 liters of water in the tank. Besides, each additional common goldfish past the first one will require a minimum of 12 extra gallons of tank space. While with the same amount of water, you can keep up to 4 small goldfish such as fancy.

With this formula, two common goldfish need 42 gallons of space at a minimum, which means roughly 168 liters of water. If you want to have three, add an extra 12 gallons or 48 liters to that, or 216 liters of tank space.

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Determine What Is The Type Of Two Goldfish In A Tank

Why do you need to do that? Your goldfish tank size depends on whether you have a fast-swimming, slim-bodied goldfish like a Common, Comet or Shubunkin, or a slower-swimming fancy goldfish.

Last but not least, adding plants to your pond will create more comfortable for our guys.

Tank Size For Common And Comet Goldfish

For two Common goldfish, Comets, and Shubunkins, a tank of at least 4 feet in length and 30 gallons in volume is recommended.

If you want your common goldfish to be truly comfortable, you’ll need an additional 20 gallons of water for each additional fish beyond 1. Consequently, two common goldfish should ideally have access to between 50 and 60 gallons of water.

Tank Size For Fancy Goldfish

Fancy goldfish require less space

Fancy goldfish are slightly smaller than common goldfish and require less space. Minimum tank dimensions for a fancy goldfish are 3 feet in length and 20 gallons in volume. If you intend to keep multiple goldfish in your tank, add 10 gallons for each additional fish. Two fancy goldfish require approximately 35 to 40 gallons of tank space and a tank length of between 3.5 and 4 feet.

Goldfish Tank Size Calculator

Here are formulas that will be helpful for you. The way to calculate it depends on which shape of your tank is.

Rectangular prism

Tank size = height * width * length

A cube-shaped tank is the same, but you just have to determine the length of one side. 


Tank size = π * (diameter / 2)² * height

For half-cylinder and quarter-cylinder, just divide above 2 or 4.

You can also use the tool that is free-supplied to save your time.

Video: Tank Size For Goldfish


Can you put two goldfish together in a tank?

Goldfish are social fish, so it is ideal to keep at least two together in a tank. More goldfish will provide companionship. They will also interact with each other in the aquarium. 

Can 2 goldfish live in a 10 gallon tank?

A 10-gallon tank for two goldfish is too small, even for small types of goldfish like fancy goldfish. The wider of aquarium space, the healthier they get. So, I recommend at least 50 gallons for Common goldfish and 35 gallons for fancy goldfish.

Do goldfish get lonely?

Since goldfish can live alone, don’t worry if they feel lonely or not. Goldfish that seem lethargic or depressed are far more likely to have a problem with their environment or health than it is that they are lonely. But if having tankmates, we’re sure your goldfish can be happier. 

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