How Many Fish Can Be in a 30 Gallon Tank and Be Comfortable?

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“How many fish can be in a 30 gallon tank?” is a question with various answers. All fishes have different sizes and growth and need different habitats.

Thus, the number can be anywhere between 1-30. Read this care guide to know how many fish can stay in a 30-gallon tank and see more interesting facts.


  • How To Calculate How Many Fish You Can Add to a 30 Gallon Tank?
  • What Affects the Number of Fish in a 30-Gallon Fish Tank?
  • What Number of Different Fishes Can You Put in a 30-Gallon Aquarium?
  • FAQs
  • Conclusion

How To Calculate How Many Fish You Can Add to a 30 Gallon Tank?

To calculate how many fish you can add to a 30 gallon tank, you can use the one-inch per gallon fish rule. According to it, you can keep one 1-inch fish in one gallon of water. However, factors such as fish species, plants, decorations and others can affect the number.

According to standardization, people believe you should stock 1 inch of fish per one or two gallons of water to allow them to survive and grow. This means that a 30 gallon fish tank can house 15 or more 1-inch fish. But this standardization can be vastly wrong and has many flaws.

Moreover, there are new and better stocking ideas at present. This rule does not take into consideration the size of the fish, the type of the fish, the aquatic plants, crystals, stones and multiple other factors. If you keep following this standard thumb rule, you can end up with a lot of sick or dead fish.

Putting four shark fishes together in one 30-gallon water tank is never a good idea. But you can also put more than 15 neon tetra fish in a 30-gallon tank because they are very tiny. There are an endless number of aquarium fish types, and they all need different-sized gallon aquariums.

For example, if you’re wondering how many 2 inch fish in a 30 gallon tank you can keep, the answer can be anywhere from five-six to 15. ‘How many fish in a tank calculators’ are also becoming quite popular, so you can use one of these for the particular fish species you intend to keep.

What Affects the Number of Fish in a 30-Gallon Fish Tank?

The number of fish in a 30-gallon fish tank can be affected by factors like fish size, type, space, amount of waste, heating system, etc.

In addition to specific sizes, each fish has different social behavior and temperament, which can affect the number you can add to the same tank.

– Size and Type of the Fish

Freshwater and saltwater fish can not live in the same tank, even if they’re small. All the fish living in the aquarium should be adapted to similar water conditions. So you can calculate how many fish in a 30 gallon saltwater tank you can fit, just don’t add freshwater fish as these will most likely die due to the high salinity.

Also, if the fish is too small, like neon tetra, you can keep 10-15 in one 30-gallon tank. But if they are large goldfish, it is better to keep only 2-3 in the same size tank. For even bigger fish like freshwater angelfish, you’d need 55 gallons, while for discus, you’d actually need a 75-gallon tank.

You also need to remember that the small size of the fish when you buy is not its final size. It will grow, and you need to have enough space to allow space for growth. You can also closely monitor the tank to stay updated about its growth.

– The Fish Tank Filter System

A proper filtration system is essential for fish to grow and live in any water tank. The filtration system and the polishing stones in the tank determine this. Many fish varieties, like the Zebra Danios, need very low maintenance . But some fish varieties are very sensitive towards the cleanliness of the water. Hence, one single water filter may not work for them.

– Amount of Waste

The amount of waste the fish generates also determines the number of fish you can raise in a tank. Plecos excrete a lot and can cause a lot of dirt in the water. So if your fish produces a lot of dirt, you should not add more than 3-4 fish in one 30-gallon tank to avoid excess waste. This also helps the fishes have enough breathing space.

– Swimming Space

There are many fish that do not move much and love to float at the surface or lay at the bottom. But fishes like Goldfish love to swim around and stay active. Hence, if you are keeping such swimmer fish, it is best to keep 2-3 of them in one 30-gallon tank.

The biggest fish for 29 gallon tank, like many cichlid species, would actually need more space, and you also need to consider that keeping a few smaller schooling fish together also requires plenty of hiding spots, which imply even more space.

– Aquarium Heater

Every fish survives in a different kind of temperature, depending on their natural state. This means that if there is no air pump or heater inside the tank, the atmosphere can become oxygen-deficient and heat up. This can kill some fish. So, it is always better not to overcrowd the tank when your fish needs a cooler temperature.

– Aquatic Plants and Crystals

Aquatic plants, crystals and stones are essential for any aquarium. They improve the aesthetic factor, act as natural polishing agents, and create oxygen within the water. But if these elements take up a lot of space inside the fish tanks, you should not keep too many fish inside. Always make sure there is enough swimming space for the fish.

What Number of Different Fishes Can You Put in a 30-Gallon Aquarium?

The number of different fishes you can put in a 30-gallon tank can vary, as each species needs a different amount of space to grow. You can keep multiple fish, such as neon tetras, while you cannot place too many cichlids in the same tank as these are larger.

So, here are a few 30 gallon aquarium fish suggestions and the number of fish from each variety that can live comfortably.

– Neon Tetra

Neon tetras are some of the best schooling fish and have multiple splashes of colors. That is why they are one of the most readily available aquarium fish options. Most of these fishes are very small and remain within 1-2.5 inches. So, 30-gallon tanks can house around 14-18 neon tetra fishes.

– Cory Catfish

You can keep around six to eight cory catfish in a single 30-gallon aquarium. These fishes are swimmers, so they need space to move around.

– Cherry Barb

Cherry barbs are also schooling fish. Hence, they need to stay in groups.

You can keep around five or six of them.

– Dwarf Gouramis

They are about 2.5-4.5 inches long. You can keep around eight or ten of them in one 30-gallon tank. They also move and travel in small groups, so it is crucial to keep at least 4 of them.

– Betta Fish

If you want to make a siamese fighting fish or betta sorority tank, keep around 6-8 female betta fish in a 30-gallon tank.

– Guppy

Guppies come in different sizes and range between 0.6-2.4 inches. How many guppies in a 30 gallon tank can live comfortably? You can keep around 12-18 guppies in one tank, depending on their growth rate.

– Cichlids

This fish comes in multiple sizes. It can range between 2-8 inches and can even go up to 3 feet.

You can keep 2-3 of the small ones in one 30-gallon tank, but the bigger one can not be fitted in this.


– Which Fish Varieties Can Not Live Together in a 30-Gallon Water Tank?

Some fish varieties that can not live together in a 30-gallon water tank are some species of sharks, mormyrids, knife fish and other territorial and other aggressive fish varieties. Unlike guppies and neon tetras, these species are not very adjusting and can not live together in a small tank.

– Can Two or Three Goldfish Live in a 30-Gallon Tank?

Two or three goldfish can live in one 30-gallon tank. But goldfish are swimmers, and they love to travel around in the free space, so when you are getting a goldfish, always try to get a bigger tank size. This keeps the fish healthy and happy.

– Can Guppies Stay with Neon Tetras in a 30-Gallon Tank?

Yes, Guppies and Neon Tetras can cohabit in a 30-gallon tank. They are both small, popular, readily available, and can be great tank mates. However, keep in mind that these are social fish, so you should keep at least two-three guppies and six neon tetras together.


The number of fish that live in one 30-gallon tank can depend on multiple factors. Today we learned a lot about these factors and other important facts.

Here is a quick recap of what we learned to help you with your pet fish journey:

  • The size and type of the fish decide the number of fish in one 30-gallon tank. But factors like aggressiveness, water filters, aquatic plants, and decorations also play a role.
  • Small fishes like neon tetras can be kept in bunches in a 30-gallon tank. You can keep around 12-18 of these fishes because they do not grow much in size.
  • But you can only keep around 2-3 goldfish or 7-8 cory catfish in the same 30-gallon fish tank.
  • If your fish do not have the same oxygen, habitat, and temperature needs, it is best not to keep them in the same 30-gallon tank even if there is enough space.

Remember to keep these factors in mind the next time you plan to rearrange your fish.

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