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How Many Fish Can I Put in a 55 gallon Freshwater Tank?

4 min read

Keeping fish in an aquarium is a great hobby. Several advantages come with keeping fish too. It relieves stress, improves your health, and also makes your home or office more beautiful.

Some people will find that the bigger the tank, the greater effect the aquarium has. One of the most popular sizes for a big tank is a 55 gallon tank. The easiest tank to start with is a freshwater tank.

55 gallon tank

If you have a 55 gallon freshwater tank, the first question you will ask is, How Many Fish Can I Put in a 55 gallon Freshwater Tank?

The rule of thumb is to keep one inch of fish per gallon of water. That is, for every one gallon of water you have in your aquarium you are permitted to put an equivalent of 1 inch of fish. In this case, where you have 55 gallons of the freshwater tank, you can put up to 55 inches of fish in it.

However, it is not as simple as this as many other factors will also influence this decision. For instance, having a 55 gallon freshwater tank does not mean that you will fill it with 55 gallons of water.

This will also influence the number of fish that it can contain. Also, the type of fish you want to put in the aquarium will determine the number that it will contain. For instance, it will be easier to add smaller fish in a large number than bigger fish.

One major advantage of having a 55 gallon tank is its size. Anyone can take care of this tank successfully because of its large size. There is enough volume of water which does not easily build up dirt.

As much as a 55 gallon tank allows you to keep many fish, you should not fill the tank to its full capacity.

That is, you should not put up to 55 inches of fish in the tank. This will allow for the build-up of pollutants and can make the water polluted thereby killing the fish.

A good population of fish to keep in an aquarium of this size that will help with pollutants is about 4-5 bottom-dwelling fish together with 2 algae eaters.

It is best to keep fish that can live together without fighting each other. Some fish are aggressive and keeping gentler fish will be detrimental. The more active fish will bully the gentle ones and may even kill them. You can keep fish such as rainbow fish, tetras, or female bettas that can live peacefully with other fish.

Water Filters in a Freshwater Tank

Another reason why this rule of 1 inch to 1 gallon of water does not always work is because of water filters. Water filters help to remove dirt particles from the water. They also remove pollutants that have been dissolved in the water such as nitrates and nitrites.

Depending on the quality of the water filter in your tank, it may be able to contain more fish than it would have without a filter.

The main reason why it is advisable to keep a smaller population of fish is because of the build-up of dirt. But with a water filter, the dirt will be removed as soon as it is introduced into the tank.

freshwater tank

There are also biological filters composed mainly of bacteria that break down the harmful nitrogenous chemicals being introduced through the feces of the fish.

When you want to introduce a fish to your tank, it is best to introduce about 2 or 3 at first. This is to allow the bacteria community to mature and be able to properly break down the nitrogen waste.

When the bacteria community has stabilized, you can then introduce more fish. You should monitor the nitrites and nitrate content daily using their respective meters to know when it is stable.

Stocking Density

Stocking density is the number of fish that can be found in a given volume of water. In our case, it will be the number of fish that can successfully live in a 55-gallon tank.

We already established that the right number will be 1 inch of fish to 1 gallon. However, the tank should be filled to only about 80 percent of its capacity. This will be about 44 gallons of water. That means a 55 gallon tank will be able to take up to 44 inches of fish.

Another thing you need to know before stocking your tank is that fish do not have the same size and shape. That means if you have a slender fish like the Zebra Danios, which has a body length of 10 inches, you will be able to stock more of them.

You cannot, however, stock more of a fish like a goldfish which also has the same length of 10 inches. This is because of their shape and body size. And you should also know that fish with larger body sizes tend to produce more waste and will pollute the water faster than slender fish.

With this in mind, you can always stock more slender fish of the same length than chubby fish of the same length.

You already know that it is impossible to fill a tank to its maximum capacity. That is, 55-gallon tanks will not necessarily hold 55 gallons of water. It is also important to note that other things are taking up space in the tank.

freshwater tank

For example, the substrate such as sand, gravel, rocks, and plants in the tank. Some tanks also contain lighting and other forms of decoration. Always consider the things found in the tank before deciding the number of fish you want to stock inside because the volume of water in a tank can be reduced up to 15 percent by the presence of these materials.

Conclusion

The rule of 1 inch of fish to 1 gallon of water is a safe rule to follow to figure the number of fish to stock.

Before stocking your tank with fish always consider:

  1. The type of fish
  2. The space available
  3. The filtration in your tank
  4. Additional substrate

Written by:

Pet Aquariums

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