How Many Fish In A 75 Gallon Tank

How Many Fish In A 75 Gallon Tank

Some fish species need a tank all to themselves, like bettas, but others like guppies do well in small schools if they have a large enough tank. Choosing the right tank size can significantly impact your pet’s life by offering them more space and less stress.

How many fish in a 75 gallon tank? I’ll explain so you don’t overcrowd your fish, causing them to compete for resources like oxygen.

A 75 gallon fish tank can hold 75 small, one-inch long fish or 25 fish that are three inches long when fully grown. The guideline for stocking a fish tank is to have one gallon of water for every inch your fish is long, measured from the snout to the beginning of the tail. This helps avoid overcrowding and bullying.

How Many Fish In A Tank Calculator

The ‘one inch of fish per gallon of water’ method works well enough to give you a rough idea of how much space a fish needs. Unfortunately, that’s oversimplifying things.

If your fish are still growing, or you want them to have babies, you’ll need more space and maybe more tanks. I’ll help you calculate how many fish to put in your tank.

Size of Fish

First, you need to know the size of your fish. As Wikipedia points out, “Standard length (SL) is the length of a fish measured from the tip of the snout to the posterior end of the last vertebra or to the posterior end of the midlateral portion of the hypural plate. Simply put, this measurement excludes the length of the caudal (tail) fin.”

Happily, pet stores can generally tell you how long their fish are. Otherwise, you’ll need to hold up a ruler, preferably when the fish is sleeping near the side of the tank, and measure.

I prefer to add a half-inch to be sure the water distortion is accounted for.

How To Tell Your Tank Is Overcrowded

If you begin to notice fish hiding from each other, you may have too many fish. Signs of outright bullying like damaged fins are another critical indicator.

However, when fish crowd around the filter or always near the top of the bank, they may be competing for air. If this happens, you almost certainly have an overcrowded tank.

Fish For 75 Gallon Freshwater Tank

Not every kind of fish does well in a 75 gallon tank. Fortunately, plenty of species thrive in these medium-large tanks, such as freshwater Angelfish, Dwarf Cichlids, Goldfish, Jack Dempseys, and Oscars.

Below I’ve created a couple of tables for different options in this tank size.

Small Fish

FishNumber of FishDescription
Guppies50 – 75Guppies stay small, but they are prolific breeders.
Danio75 – 150Danios are tiny schooling fish who prefer living in groups.
Chili Rasboras75 – 150Chili Rasboras are brightly colored small fish that can live two to a gallon
Tetras50These brightly colored fish are content to swim in larger schools.
Dwarf Cichlids20 – 25Dwarf Cichlids don’t often grow over four inches, and they are generally happy in schools.

Larger / Solitary Fish

FishNumber of FishDescription
Bristlenose Plecos1 – 2This species doesn’t share well with each other, though they can sometimes thrive with other fish.
Tinfoil Barbs1A single Tinfoil Barb is enough for this tank size.
Fancy Goldfish4Fancy Goldfish prefer to live as a pair, or at most two pairs.
Oscar1Oscars make bad neighbors for each other. It would be best if you had at least a hundred-gallon tank for two of these.
Jack Dempseys1 – 2Male Jack Dempseys can get up to a foot long.

Large tanks are also a great way to get a mix of fish together. Choosing species that complement one another and can live well together is a challenge.

Here are a few ideas to help you get started.

Multi-Species Tank Ideas

Small Colorful Choices10 – 20 Tetras (Your choice of colors)20 – 30 Chili Rasboras1 Oscar as a statement piece 
  Not For Beginners10 – 20 Silver Hatchetfish & Tetra10 Sterbai Cory8 Platys1 Rubberlip Pleco
Simple & Lovely2 – 4 Angelfish2 German Blue Rams30 Celestial Pearl Danio 

How Many Fish Can Live In A 75 Gallon Tank

Selecting fish can be a lot of fun if you know how many fish can live in your 75 gallon tank.

The species and size of the fish make a considerable difference because some fish don’t tolerate neighbors, and others need a school to be happy.

It’s worth the effort, though, because when you finally get that perfect tank setup, it brings the room together.

How Many Saltwater Fish In A 75 Gallon Tank

Saltwater fish have different needs than fresh, and there’s more to it than adding salt. Many species also require warmer water and more space.

According to The Beginners Reef, “Fish stocking guidelines for saltwater aquariums are 1″ of fully grown fish for every 5 gallons of water volume.”

Sadly, if you add too many fish, it’s almost sure that some will die. Not only will you need to clean much more often to keep your fish healthy, but they may have trouble breathing.

Oxygen in any tank is limited, and even a great filter can’t provide for too many fish inhaling in the same space.

How Many Mollies In A 75 Gallon Tank

Mollies are schooling fish. You can fit more of them together in a 75 gallon tank. You can have up to a hundred with this species, making them one of the most prolific options for people who want a single species.

However, you need the right blend.

When creating your school of mollies, it would be best if you had two females for every male. Setting them up like this will help prevent fighting among the males.

How Many Angelfish In A 75 Gallon Tank

In a 75 gallon tank, you can have a maximum of 4 to 6 angelfish. However, this breed needs lots of decor so any bullied fish can hide.

Angels will pick on each other, so it’s essential to avoid overcrowding and ensure that there are various plants and features for these beautiful fish to explore.

How Many Oscar Fish In A 75 Gallon Tank

Unless you are breeding Oscars, please do not put more than 1 in your 75 gallon tank. Oscars can live with other fish, but they don’t share well with their own species.

These unique fish will get up to ten inches long and can occasionally be bullies to smaller fish and eat any species it can fit in its mouth, so regular feedings are essential if you plan to keep one.

It’s also a good idea to provide lots of hiding places for other fish to escape where your Oscar won’t fit.

How Many Rainbow Fish In A 75 Gallon Tank

You can have up to a dozen rainbow fish in a 75 gallon tank. Notably, this species won’t do well with others, so choosing a dozen rainbow fish means you only keep these twelve fish in the tank.

Moreover, if you add more than a dozen, you’ll find the water quality quickly goes down, requiring more cleanings, and it’s likely that you’ll start to see some fish getting bullied since there’s not enough space for all of them.

How Many Discus Fish In A 75 Gallon Tank

Discus fish are highly territorial, and they get aggressive with each other. You can keep up to a dozen discus; however, they need to be very near to the same size.

Any smaller or weaker seeming discus will quickly become the subject of the other’s aggression. It’s usually better to choose just one of this species.

According to Planted Tank, “It is possible, BUT you risk inviting some serious aggression/harmful pecking order behavior and resultant problems. Keeping just 2 or 3 often results in 1 or 2 of them being badly mistreated by 1 or 2 others, which produces a lot of stress and may well result in a fatality.”

How Many Fish In A 75 Gallon Reef Tank

Reef tanks need a lot of decor, and they don’t accommodate very many fish. At most, you may be able to have 7 fish if none of them are too large.

Too many fish in this type of tank will pollute the water and cause competition for prime real estate. You could quickly end up with battling fish even among ordinarily calm and docile species.

How Many Betta Fish In A 75 Gallon Tank

Choosing betta fish for your 75 gallon tank is an unusual option. Most people mistakenly think these fish belong in tiny spaces, but they do well in large tanks.

The problem is that male bettas are incredibly aggressive, which is why they’re called ‘fighting fish.’

You might be able to put two male bettas in a tank this size because there’s enough space. It’s risky at best.

Alternatively, if you want female bettas, you can have three or four, but they lack the long showy fins of their male counterparts.

How Many Tetras Can I Put In A 75 Gallon Tank

A large school of up to 50 tetras will be happy in a 75 gallon tank. Choose neon tetras for a brilliant, colorful display that works well with other fish, though you’ll want a slightly smaller school if you add other species in the same tank.

These small, brightly colored fish are prized for their looks, and they are fantastic starter fish that are easy to care for.

Helpful Tips To Know About How Many Fish In A 75 Gallon Tank

When filling a 75 gallon tank with fish, the right mix and quantity of fish are vital. Likewise, learning about decor and how to set up a suitable habitat for the fish you want can make or break your tank.

Here are more helpful tips to know about how many fish in a seventy-five-gallon tank.

  • Clownfish are one of the most popular choices for fish tank owners because they are beautiful and highly recognizable. However, this species doesn’t enjoy the company of its peers. Only add 1 or 2 clownfish to your tank.
  • If there is a type you want more than any other, start with that species and add other creatures and decor that suit its lifestyle. Doing this will ensure you get the fish you love instead of settling for a species that fits what you already have.
  • Like other tanks, you need to clean your 75 gallon tank weekly or bi-weekly, depending on how close it is to maximum capacity. More fish means more cleaning. Sadly, if you overstock your tank, you will lose fish no matter how much you clean, and in the meantime, the water quality will worsen until enough fish are gone.

Final Thoughts

Deciding how many fish in a 75 gallon tank is just the first step. You also need to check every species to see that they live well together, or you’ll end up with a lot less fish than you began with.

Plus, lousy tank mates make for stressed fish, and that means health problems.

Still, depending on your tastes, you could have a large school of small fish, a stunning combination with twelve to twenty mid-sized fish, or a couple of eye-catching beauties from a larger species in your tank.

Ted Smith

My name is Ted Smith and I’m the creator of I have a passion for educating people about animals and wildlife. I have been working with the National Wildlife Federation for the past 10 years and I became a wildlife blogger to help people become excited about animals and encouraged to care for these wonderful creatures.

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