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How Many Fish In A 20-Gallon Tank? (Best Fishes Guide)

How Many Fish In A 20-Gallon Tank? (Best Fishes Guide)

You might soon upgrade your home fish tank from a 5-gallon tank to a 10-gallon tank and then from a 10-gallon tank to a 20-gallon tank if you’re a dedicated and enthusiastic fish keeper. 

Maintaining a fish tank indoors, changing the water, feeding the fish, and relaxing after work can help to calm anxiety, which is beneficial for both physical and mental health. So the question is, how many fish should be kept in a big 20-gallon tank?

Do you have difficulties filling a nano tank? Are you wondering about how many fish a 20-gallon tank holds? Even seasoned fishkeepers frequently struggle when there isn’t enough room. Moreover, there are simply so many varieties of pet fish to pick from! 

A 20-gallon tank has the capacity to house around 19 to 20 1-inch fish or ten 2-inch fish. Note that this is as per the 1 inch of fish per gallon of water idea. However, you shouldn’t follow it for large fish species around 3-4 inches due to their increased volume. 

How Many Fish To Keep In A 20-Gallon Tank?

How many fish can you keep in a 20-gallon tank? This might be a question you have if you’re new to keeping fish. First of all, a fish tank should never contain more fish than one inch in length. While this recommendation is correct for tiny fish, it is wholly incorrect for larger species. 

This article will go over the factors to take into account while selecting a wide range of fish for your home aquarium. You’ll be able to maintain wholesome, content pets in this way!

You may need to add more liters of water to the tank, depending on the type of fish you have. The size of the fish you want to add should also be taken into account.

For example, Platys can grow to about two inches, making them suitable for 20-gallon tanks. These tiny fish like to be with other species despite their size. A 20-gallon tank is an ideal size for housing either one or two of these adorable animals. 

Additionally, think about the kind of fish you wish to keep. If you like, you can maintain up to 20 little tetras there in the aquarium, but you’ll need to make the changes accordingly if you’re raising a loner kind of species. 

The size will determine how many fish fit in a 20-gallon tank because larger species produce more waste and require more space. 

Extra care is required since healthy fish may grow quickly—some can gain up to two centimeters each month—so you should provide adequate room for your pet fish to expand.

Which Fish to Keep in a 20-Gallon Tank?

Fish Type  Number Of Fish Suitable In A 20-Gallon Tank
Guppies 10
Platys  10
Mollies  2
Swordtails  2 (maximum 3)
Cory Catfish 4
Bristlenose  1
Otocinclus  6
Kuhli Loach 2
Fancy Goldfish 1

Best Fish To Keep In A 20-gallon Tank

The possibilities with a 20-gallon aquarium are fascinating. With a tank this size, you can have real plants, a variety of stunning freshwater fish, fascinating creatures, and all of this without using up a lot of room. But like any aquarium, you need to supply it carefully if you want it to prosper.

More considerations than just understanding which fish mature to the right size go into selecting the best species for a 20-gallon aquarium.

Whatever fish that you stock should be compatible with one another, and you should also take into account their personalities and demands.

These listed species are excellent communal fish. The majority are tranquil, although a few can occasionally display a mildly violent side. Do more research prior to putting them in the tank to make sure they get along well with the other fish you plan to keep. 

Without further delay, here’s the list of fishes that would be best for your 20-gallon aquarium.

1. Swordtails

SwordtailsThough smaller and sleeker, swordtails resemble platies in appearance and disposition. You only need one male to every two females, just like platies. This lessens the strain on the females whenever the males start bugging them and acting a little frisky.

The sword-like tails of male swords make them easier to identify. Fish store personnel may need some instruction when you are choosing your fish because you can encounter those who don’t even know how to couple platies.

2. Dwarf Gourami

Dwarf GouramiOnly fish here on the list that would classify as occasionally being semi-aggressive are Dwarf Gouramis. They can make wonderful communal fish because they are lovely and generally quiet. If you have a pair, though, they might fight or one might harass the other.

Try to avoid keeping two male fish in the same tank to lessen the likelihood of this happening. In order to give a fish being bullied a place to hide, it’s also a great idea to incorporate some excellent hiding places in your aquarium.

3. Mollies

molly fishThere are numerous types of molly fish, including the lyretail molly, sailfin molly,  marble molly, and one of the most loved fish, the black molly. You want at least two females to every male, just like with platies and swords, and you can determine the difference using the same technique as with platies.

Since none of these fish lay eggs, they are all livebearers. It moreover means that one morning you might awaken to find baby fish playing in your tank!

4. Neons And Other Additional Tetras

Neon TetraLike neons, the majority of tetras are gentle, little fish that should be housed with other species of the same kind. A group of twelve or more neon fish in a lush tank looks wonderful, but at least six should be present.

You may want to think about other tetra species as well. Cardinal tetras and Black neons are two examples of fish that resemble neons in size and behavior. Others, like black-skirt tetras, are a little larger.

5. Fancy Guppies

Guppies & MolliesAmong the most attractive and vibrant fish, you can keep in your 20-gallon tank are the Fancy Guppies. Considering that they are livebearers, aim for two females for every male. When keeping livebearers, you should always try to keep a total of each fish that is divisible by three.

These adorable creatures are going to be all over your tank. But don’t worry. They are too little to cause many difficulties. Despite their high activity level, guppies make ideal tank companions for other tiny community fish as they are really peaceful.

More: How Many Guppies in a 20 Gallon Tank?

6. Harlequin Rasbora

Harlequin RasboraThese are colorful, attractive fish that need to be kept in groups of at least six. They are calm community fish, and their striking orange or red hues contrast beautifully with their black sides.

Ten harlequin rasboras along with Ten neons in a well-planted 20-gallon tank would look wonderful! All of the tiny fish suggested here should be maintained alongside other tiny, peaceful fish as they might serve as lunch to larger fish!

7. Otocinclus

Otocinclus CatfishOtocinclus are among the top algae eaters for tiny aquariums and are adorable little shoaling fish. They have a pleco-like appearance and exhibit a similar level of adhesion to embellishments and glass.

However, they remain small, and you can keep a group of about a dozen in a 20-gallon tank, unlike plecos. However, to make sure they all have food to eat, we’d advise keeping their numbers between 6 and 8. In keeping with that, you should add algae wafers to their food as a supplement.

8. Zebra Fish

Small, tough tiny striped fish are called zebrafish. Although they are essentially minnows, they have a tetra-like appearance. They are among the greatest tropical fish for beginners since they are so simple to care for. Additionally, they are lively little fish that is a lot of pleasure to keep in a tank.

These are shoaling species that should be maintained in bunches of at least six, just as tetras. When fish feel threatened, this social habitat helps to lower stress and maintain fish health.

9. Corydoras

Corydoras-CatfishCory catfish are excellent additions to any aquarium 10 gallons or larger because they are bottom scavengers. These tiny creatures will aid in keeping your tank tidy. 

Although you should offer some sinking pellets to ensure they receive enough to eat, they will consume any remaining fish food which settles towards the bottom of your tank. 

They must be maintained in bunches of at least six since they shoal. You might take into account a few distinct types for a 20-gallon tank.

10. Platy

platyFish such as platies are lively and entertaining to watch. They come in a number of attractive variations, such as the Mickey Mouse platy, which appears to have iconic and adorable bunny ears on its own tail.

Ideally, there should be at least 2 different females for each and every male. By observing the fin beneath their stomachs, you can distinguish males from females. Male fish have pointed fins, whereas female fish have wide, flat fins.

Which Large Fish Are Suitable For A 20-gallon Aquarium?

We’d strongly suggest that you think about getting a 55-gallon or larger tank if you plan to keep huge fish in it. Stocking a 20-gallon tank gives you more alternatives than a 10-gallon tank, but there are still restrictions.

Here are some large fish to keep in a 20-gallon aquarium. 

The Angelfish

As long as you don’t add much additional fish, you could keep a pair of angelfish in a typical 20-gallon aquarium. However, It would be really better to keep them in a 55-gallon or larger aquarium. As adults, angelfish will consume small fish like tetras and guppies because they grow much larger than most people are aware of.

The Goldfish

One goldfish may be kept in a 20-gallon tank at a time, and no other fish should be kept. Goldfish require special maintenance, and can easily grow significantly in size. 

More: How Many Goldfish in a 20 Gallon Tank?

Which Popular Fish Won’t Fit in a 20-Gallon Tank?

There aren’t any pleco species suitable for a 20-gallon aquarium. Even comparatively smaller species, such as rubber-lipped plecos, need at least a 30-gallon aquarium. The common pleco is only suitable for really large aquariums because it can grow to be a couple of feet long.

There are also other fish like Bala sharks, silver dollars, and tinfoil barbs. When such fish are young, they are shiny and alluring, but as they become older, they all get too big to fit in your tank. 

Best Combinations for a 20-Gallon Tank

In spite of the fact that you can have a wide variety of fish in your aquarium, not all fish species will do well in a 20-gallon tank.

Additionally, not all of these can coexist in harmony. As a result, it’s critical to understand which species to group together and which to omit. Here are a few combinations of freshwater fish you could try:

Combination 1:

You can begin by adding some eye-catching species like mollies, guppies, and platies. Then you can add a swarm of Black Phantom tetras, Neon Tetras, and  Glowing Tetras. 

At the ground level, you can add Dwarf Corydoras species including the Skunk Corydoras Catfish, Panda Corydoras Catfish, and Albino Corydoras Catfish.

Combination 2:

Keeping the same categories, you can add a pair of male and female species of, Electric Blue Ram German Blue Ram, or the Angel Ram for the eye-catching group of fishes.

Then you can add the warm of 8 to 10 Neon Tetras. At last, you can finish up by adding 6 to 8 Cory Catfish at the ground level.

Combination 3:

Begin by introducing some eye-catching species such as a pair of male and female Honey Guarami. Then add a swarm of varieties of rasbora fish for example Lambchop Rasbora, Glowlight Rasbora, Harlequin Rasbora, Red Dwarf Rasbora, or Dwarf Rasbora. 

At the ground level Cherry shrimp can be added but to safeguard the shrimp from fish, ensure that you provide enough cover.

Final Thoughts

After carefully evaluating the concerns and researching them, we can conclude that the optimal number of fish for a 20-gallon tank varies depending on the species of fish, but in general, twenty 1-inch fish or ten 2-inch fish can fit in a 20-gallon tank.

We also attempted to provide well-researched and best-possible responses to all pertinent topics. We really hope that we were able to provide you with an overview of the number and types of fish to keep in a 20-gallon tank.