How Many Fish in a 75 Gallon Tank? – Tank Calculator

how many fish in a 75 gallon tank

How many fish in a 75-gallon tank? Let’s calculate. The rule states a ratio of 1:1, meaning that a 1-inch fish can occupy 1 gallon of the tank.

This could hold true for a small goldfish. However, a bigger angelfish that can measure up to 3-5 inches might have a different story. On average, depending on the breed, a 75-gallon water tank might be expected to accommodate up to 30 fishes.

Fish Type and Size Matters


Filling your aquarium with the appropriate number of fish for a 75-gallon tank is detrimental in achieving their optimum health. It also matters if it’s a freshwater fish, saltwater fish, or something else, so you can predict the rate of their growth and their behavior.

It is critical to familiarize yourself with fish type and its sizes in order to make sure that their growth will be worth your investment. Some can grow as big as 4-5 inches while some can remain 1-inch long for the rest of their lives.

Among the favorites of hobbyists are as follows:

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Fish TypeSize (inches)Recommended stocking
Mickey Mouse Platy1.5 – 215 – 20
White Cloud Mountain Minnow1.520 – 25
Zebra Fish210 – 15
Guppies225 – 30
Serpae Tetra1.7525 – 30
Pea Puffer1 – 1.510 – 12
Swordtail3 – 410 – 12
Dwarf Gourami28 – 10
Black Ruby Barb2 – 310 – 15
Beacon Fish212 – 18


If you plan to mix two to three breeds in one tank, do your own research first. It is best to quarantine them in separate tanks for 4 weeks before introducing them together to avoid any untoward distribution of disease.

Which Breed Goes Together?

For 75 gallon stocking ideas to create a healthy fish commnity for your tank, consider the peaceful ones that go well together. Considerations would include the environment, type of fish, its size, fish personalities, and other plant decors. Among the best partners are as follows:

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  • Green Neon Tetra and Apistogramma – these two are a beautiful contrast of motion as apistogrammas stay mostly at the bottom of the tank while green neon tetra on the upper half.
  • African Cichlids and Synodontis Catfish – these two are a dance of colors. The bright neon hues of African Cichlids appear to pop out in the background of the darker hues of black and golden brown of Cichlids.
  • Cherry Barbs and Guppies – their varying motions and great color combination of bright red and gold can be appreciated well in aquariums, even when viewed from afar.
  • Red Hook Silver Dollar and Pictus Catfish – Red Hook Silver Dollar usually inhabit the upper portion of the tank and are swift to swim across edges. Pictus Catfish, on the other hand, provides the slow, stable pace occupying the lower bank of the tank.


You can play with these partnerships and see which 75 gallon fish tank ideas will fit your home well.

The Ideal Stocking Rate


On average, with a 1-2 inches tropical fish per gallon, you can stock up to 30-35 in one tank. However, it’s recommended to keep 20 – 30 fish, depending on the species and sizes.

75-gallon freshwater tank stocking ideas:

You can keep guppies, cory catfish, mollies, Neon tetras, platies, and Khuli loach in a 75-gallon freshwater aquarium. The total number of fish should be at most 25, as fish will generate waste and even become territorial when not having enough space to swim around.

75-gallon saltwater tank stocking ideas

Fish that thrive in saltwater conditions include Dwarf Angelfish, Orchid, Neon Dottyback, Squirrelfish, Squaretail Bristletooth, etc. Indeed, it’s important that you consider giving each fish 2 – 5 gallons of water, depending on their sizes and living requirements.

Furthermore, the health of your aquarium should take into consideration important factors like the filtering system and the amount of plants and decorations.

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  • Filtering System


Avoid fully stocking your 75-gallon tank with more than it can handle. Remember there should be less than ¼ of your total intended number of fish to stock that should be introduced to the tank at once.

Doing this will minimize the toxic waste that will accumulate in the aquarium in a short amount of time. Consequently, you can also have better monitoring and maintenance of its filtration system.

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  • Amount of Plants and Decorations


Plants and decorations take up room that’s supposed to be for your chosen fish breed. Systematically designing your aquarium with just enough plants to provide a playground for your nano fishes while not overcrowding the tank, is the best way to go.

Frequently Asked Questions


What fish can live together in a 75-gallon tank?

Given the surface area, stocking a 75-gallon tank can be a challenge. Among the easiest to combine are angelfish, rainbowfish, cichlids, gouramis, and livebearers. Most of them live well in an aquarium filled with plants as they do not eat them.

How many Discus in a 75-gallon tank?

About 7 discus fish can be in a 75-gallon tank, as each of them will need 10 gallons of water. They’re quite big, so it’s easier to fill the tank and take less to maintain.

How often do you need to clean a 75-gallon fish tank?

With a huge tank, it is best to clean it at least every two weeks. Depending on the quality of your filtering system, you can extend cleaning it once every month. Just watch out for water changes and dirt accumulation along the corners of the glass.

Which is better – more small fish or less big fish?

It actually depends on your 75-gallon aquarium ideas. However, small fish could mean faster accumulation of toxic waste that could deter the overall health of the group.

Big fish, on the other hand, would be expected to have a bigger mess to clean that could clog your filtration system. Be very keen in calculating how many gallons per fish is allowed.


Exactly how many fish in a 75-gallon tank? That depends on the type and size of fish stocked. Stocking 0.5-1 inch fish can fill your tank with up to 80 crowded schools of fish. Stock it with twice or thrice its size and you’re down to a maximum of only 35.

You can mix and match them too depending on their behavior and level of attractiveness. Stocking a 75-gallon tank can be the most satisfying hobby you can start any day.

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