Are you setting up a new 20 Gallon Tank? Wondering how many fish can fit in your aquarium? The rule of thumb for determining aquarium stocking level is a gallon of water can hold one fish that is 1 inch long. **That means, in a 20 gallon tank, you can have 20 one-inch fish.**

However, that is just a rule of thumb, there are many factors that affects how many fish can go in a 20 gallon tank. Due to these factors, expect to end up with less than 20 fish in your 20 gallon tank.

## Factors to Consider for Stocking 20 Gallon Aquarium

The 3 questions you need to ask yourself when it comes to stocking your 20 gallon aquarium are 1.) What is the Adult Size of your Fish? 2.) Can you Maintain Good Water Quality? and 3.) Will You be Breeding Fish? The answer to these questions will help you determine how many fish can go in your 20 gallon tank.

### 1. What is the **Adult Size** of your Fish?

Find out the adult size of the fish you are buying so you can base your calculation on the adult fish size and *not* the juvenile fish size.

### 2. Can You Maintain Good **Water Quality**?

Know that the more fish you have in your fish tank, the harder it is to maintain water quality. If you plan to install a high performing filtration system, then you can get away with stocking more fish in your 20 gallon tank. You will also have to do more frequent water changes if you want to stock more fish in your 20 gallon tank. If you think you can’t maintain optimal water conditions, then it’s best to play it safe and have less fish.

### 3. Will You Be **Breeding Fish**?

If you are planning to breed fish or you know you are getting fish that breeds very easily, you should start with less fish than the prescribed 1 gallon per 1 inch. This is to avoid overcrowding in your fish tank once breeding starts.

## How Many Fish can Fit in 20 Gallon Tank?

As a rule of thumb, you can fit 20 one inch fish per 20 gallon tank. Below you will find a calculator to help you to determine how many fish you can stock in a 20 gallon tank.

Remember the number of fish you get from the calculator are for *species-only* tanks. If you plan to mix fish in a community tank, you will have to reduce the number of fish so you don’t overcrowd your 20 gallon tank.

## How Many Tetras in a 20 Gallon Tank?

You can fit 13-16 tetras in a 20 gallon tank. Tetras are small schooling and number of tetras that fits in a 20 gallon tank will depend on the exact type of tetra. Below is a table showing the number of tetras that can go in a 20 gallon fish tank.

Type of Tetra | Number of Tetras in a 20 Gallon Tank |
---|---|

Cardinal Tetra | 16 Cardinal Tetras in a 20 gallon tank |

Ember Tetra | 16 Ember Tetras in a 20 gallon tank |

Gold Tetra | 13 Gold Tetras per 20 gallon tank |

Lemon Tetra | 13 Lemon Tetras per 20 gallon tank |

Neon Tetra | 13 Neon Tetras per 20 gallon tank |

Rummy Nose Tetra | 13 Rummy Nose Tetras per 20 gallon tank |

X-Ray Tetra | 13 X-Ray Tetras in a 20 gallon tank |

## How Many Danios in a 20 Gallon Tank?

You can fit 11-16 Danios in a 20 gallon tank. The number of danios in a 20 gallon tank depends on the type of danios. Celestial Pearl Danios (also called Galaxy Rasboras) are small fish that does well in 20 gallon tank. They grow only to around 1 inch long. You can stock 16 Celestial Pearl Danios in a 20 gallon fish tank. While you can stock 11 Zebra Danios in a 20 gallon fish tank.

Types of Danios | Number of Danios in a 20 Gallon Tank |
---|---|

Celestial Pearl Danios | 16 Celestial Pearl Danios in a 20 gallon tank |

Zebra Danios | 11 Zebra Danios in a 20 gallon tank |

## How Many Goldfish in a 20 Gallon Tank?

You can fit 5 goldfish in a 20 gallon tank. Goldfish can grow big, are very messy eaters and will produce a lot of waste. It’s best not to overcrowd your goldfish. Keep 5 goldfish in your 20 gallon tank.

## How Many Guppies in a 20 Gallon Tank?

You can fit 13 guppies in a 20 gallon fish tank. However, guppies breed very easily so be prepared to move some guppies out once the breeding starts to avoid overcrowding. Otherwise, you can start with less guppies, start with 8 guppies in your 20 gallon fish tank. Get 3 male guppies and 5 female guppies.

## How Many Swordtails in a 20 Gallon Tank?

You can keep 8 swordtails in a 20 gallon fish tank. I’d get 2 male swordtails and 6 female swordtails. Do know that swordtails breed easily. You will eventually have more fish than can fit in your 20 gallon tank, be prepared to move some swordtails out once the breeding starts to avoid overcrowding. I suggest starting with less swordtails. Start with 5 swordtails- 1 male and 4 females.

## How Many Mollies in a 20 Gallon Tank?

You can keep 8 mollies in a 20 gallon tank. Get 2 male mollies and 6 female mollies. Similar to guppies and swordtails, mollies breeds very easily so be prepared to move some out once breeding starts to avoid overcrowding. Keep in mind that mollies are susceptible to diseases if the water is not slightly brackish. Once breeding starts, if your water parameters are not right, be prepared to lose some mollies.

## How Many Platies in a 20 Gallon Tank?

You can fit 10 platies in a 20 gallon tank. Get 3 males and 7 female platies. Similar to guppies and swordtails, platies breeds very easily so be prepared to move some out once breeding starts to avoid overcrowding.

## How Many White Cloud Mountain Minnows in a 20 Gallon Tank?

You can keep 16 White Cloud Mountain Minnows in a 20 gallon tank. These are hardy, schooling fish that are great for beginners. Keep in mind White Cloud Mountain Minnow are cold water fish.

## How Many Corydoras (Cory Cats) in a 20 Gallon Tank?

You can keep 7-13 Corydoras (Cory Cats) in a 20 gallon fish tank. Cory cats like to be in a group. You need at least 2 Cory Cats in a 20 gallon tank. Most Corydoras are bottom dwellers (Dwarf Cory swims in open water). You will probably want to mix Cory cats with other tankmates. If you do, you will have to reduce the number of Cory Cats in your 20 gallon tank to make room for tankmates.

Type of Corydoras (Cory Cats) | Number of Cory Cats in a 20 Gallon Tank |
---|---|

Bronze Cory Catfish | 7 Bronze Cory Cats in a 20 gallon tank |

Dwarf Cory Catfish | 13 Dwarf Cory Cats in a 20 gallon tank |

Peppered Cory Catfish | 7 Peppered Cory Cats per 20 gallon tank |

## How Many Barbs in a 20 Gallon Tank?

You can keep 6-10 barbs in a 20 gallon tank. If you are new to keeping barbs, Rosy Barbs are good for beginners. They are tolerant to a wide range of water parameters. Beware of Tiger Barbs as they tend to be fin nippers. Don’t keep Tiger Barbs in the same tank as other long finned fish.

Type of Barb | Number of Barbs in a 20 Gallon Tank |
---|---|

Cherry Barb | 8 Cherry Barb in a 20 gallon tank |

Golden Barb | 10 Golden Barbs in a 20 gallon tank |

Rosy Barb | 7 Rosy Barbs per 20 gallon tank |

Tiger Barb | 6 Tiger Barbs per 20 gallon tank |

## You May Also Be Interested In:

How Many Fish in 10 Gallon Tank? (calculator)

Easy Fish for Beginners and Lazy Fishkeepers (hardy fish)

## Everything You Need to Set-Up Your 20 Gallon Aquarium

- 20 Gallon Aquarium Starter Kit
- Hanging Filter
- Aquarium Heater
- Gravel (15 lbs for 10 gallon tank)
- Rocks: Natural rocks and/or Rock caves
- Fun aquarium Decor: Sponge Bob
- Aquarium Glass Cleaner
- Aquarium Gravel Cleaner
- Water Conditioner (dechlorinator)
- Fish Flakes

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