# How many fish in a 20 gallon tank?

If you are a devoted and avid fish keeper, then your home fish tank may soon change from a 5 gallon tank to a 10 gallon tank, and soon from a 10 gallon tank to a 20 gallon tank, right? Keeping a tank of fish indoors, changing water, feeding and enjoying after work, can relax the nervousness, which is very good for physical and mental health. So, the question is, in the face of a large 20-gallon tank, how many fish should be kept?

## Calculation of aquarium water surface area

To determine how many goldfish an aquarium can hold, you need to know the water surface area of the aquarium, and the calculation of the capacity also requires the use of the water surface area. This is easy to calculate by following the example below. The length of the aquarium multiplied by the width is equal to the water surface area, and the aquarium water surface area multiplied by the height to get the volume of the fish tank.

If the dimensions of an aquarium are: 60CM, 30CM, 40CM, this indicates a length of 60 cm, a width of 30 cm and a height of 40 cm. To multiply the length of the aquarium by the width to get the water surface area in square centimeters, for example: 60 cm x 30 cm = 1800 cm2. To multiply the water surface area by the height, you get the volume in cubic centimeters, such as 1800 square centimeters x 40 cm = 72,000 cubic centimeters. Use the calculation results divided by 1000, you can convert the volume unit from “cubic centimeters” to “liters”: 72000 ÷ 1000 = 72. So the water surface area of the tank is 1800 square centimeters, the volume of 72 liters.

So, can fish keepers decide how many fish to keep from the beginning by using the results of the “holding formula”? No, you can’t. Because it takes at least six weeks for the aquarium water environment to stabilize from the initial set up to the full. Adding a large number of fish from the beginning will make the fragile and tender filtration system can not withstand or even unable to grow, then after six weeks you can not get a stable aquarium water environment. You should start with one or two and gradually add more.

## What is the right density of fish?

So different sizes of fish tank, how to control the number of ornamental fish? Today give you a calculation method, we can follow a liter of water for 1 cm fish, for example, your tank is, 60 cm x 45 cm x 45 cm, we first calculate how many liters of water it has, calculation method, in centimeters, (length x width x height) / 1000, the result is the number of liters of water body.

Take the above mentioned 60cm fish tank as an example, the result is 121 liters of water, for example, for 3cm ornamental fish, 121 ÷ 3 = 40, then this tank can keep 40 ornamental fish of 3cm in length.

By this method above, you can calculate how many ornamental fish you can keep in your own tank, of course, this method is more conservative. Of course, we also need to consider the filtration effect, fish species, mixed breeding situation and other factors. Good filtration effect can be more, fish species can eat and pull to moderate reduction, mixed breeding than single breeding to moderate reduction.

## How many fish should be kept in a large 20-gallon tank?

If you’re new to keeping fish, you may wonder how many fish you can keep in a 20 gallon tank. **First of all, you should never put more than one inch of fish in a tank. While this guideline is accurate for nano fish, it is completely inaccurate for larger species.** This article will discuss what to consider when choosing a number of fish for your new aquarium. This way, you’ll be able to keep healthy and happy pets!

Depending on your fish, you may have to add additional gallons to the water. You should also consider the size of the fish you’d like to add. Platys are good for 20-gallon tanks because they can grow to almost two inches. Despite their small size, these little fish enjoy being in a group. A 20-gallon aquarium is perfect for one or two of these lovely creatures.

Moreover, you should consider the type of fish you want to keep. You can keep up to 20 small tetras in the aquarium if you’d like, but if you’re keeping a solitary species, you’ll have to increase the number to twenty. The number of fish in a 20-gallon tank will depend on their size, as bigger species create more waste and need more space. If you’re looking for a community aquarium, you can have up to 20 small tetras.

Extra attention is needed: fish living in a good environment may grow fast, some can grow up to two centimeters a month, so you should leave enough space for your beloved fish to grow. Finally, I wish you all can make full use of your big 20 gallon fish tank and let the right fish for your tank accompany you in your daily life!

**Related Topic:** How Many Fish in A 5 Gallon Tank?