How Many Angelfish In A 125 Gallon Tank?

The rule of thumb for fish size in a tank is one inch per gallon of water. Angelfish can get between 6 and 8 inches long and 6 to 10 inches tall. Because Angelfish also grow very tall, they need 20 gallons per fish. A 125-gallon tank would then house six Angelfish easily.

There are arguments about the number of angelfish in a 125-gallon tank, as some would believe less is best, and others believe they need more space than other fish. To understand the ratio, you will have to know the temperament of the angelfish and consider the type of tank.

How Many Angelfish Can A 125-Gallon Tank Hold Safely?

Suppose you work according to the rule of thumb; you would take a gallon of water against an inch of the fish. Adult angelfish grow 8 inches in length maximum, some could grow longer. When applying the formula, you will end up with 12 to 15 angelfish in a 125-gallon tank.

The catch with Angelfish and the space they need comes with their height. The standard formula doesn’t consider their temperament as a little feisty, and needing their own space would account for more space per fish.

When you aim to buy Angelfish for your tank, you must opt for a higher-than-average tank. For example, a tank at 19 inches or higher would be perfect for Angelfish, as their ventral fin at the bottom and dorsal fin at the top can measure 6 inches or more.

They are territorial fish who might get feisty if they compete for space and food or are too few, as they are also schooling fish. Having six or seven Angelfish in a 125-gallon tank will ensure they are happy, have enough space, and live in peace with other tank mates.

The size of your Angelfish might buy you some time and space to invest in a bigger tank when they are ready:

Size of AngelfishGallons Needed Per AngelfishHow Many In A 125-Gallon Tank
2 inches (baby)15 gallons9 to 10 babies
4 inches (juvenile)17 gallons7 to 8 juveniles
6 inches (adult)20 gallons6 to 7 adults

Can You Have Too Many Angelfish In A 125 Gallon Tank?

You can, without a doubt, have too much Angelfish in a 125-gallon tank. However, when you go higher than eight adult Angelfish, with other tank mates and accessories, you will see the consequences sooner rather than later.

Fish, especially Angelfish that don’t have enough space to swim and get away from the others, might start to act up. It is in their nature to get territorial, but the owner can quickly eliminate this by giving the appropriate amount of space.

With too little space, the feistiness leads them to argue and fight with fellow angelfish, increasing their stress levels. They might even target the other tank mates and try to eat them to free up space.

When you have Angelfish in a space too small for them to function, they will try to adapt by not growing their full size. They’ll have stunted growth, leading to them not living as long as the ten years they can.

An overcrowded tank can cause fluctuations in the temperature and pH levels of the water. Any differences in these compartments cause stress on the fish and can lead to illnesses and early deaths. Therefore, you must clean the water regularly and carefully monitor the pH levels.

Stress significantly influences the fish’s immune systems and causes them to get sick quickly. You might learn about illnesses too late, as they don’t show signs of sickness before it is severe. For example, if your fish doesn’t want to eat and looks lethargic, they might be sick.

With too little water and over-crowded fish, the debris and left-over food particles rest on the accessories and plants, decreasing the water quality and slowing down the Angelfish metabolisms.

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Can You Have Too Little Angelfish In A 125 Gallon Tank?

A 125-gallon tank is extensive and perfect to house a school of angelfish. They love to be in a group of 5 to 6 as they are schooling fish, which would keep them happy.

Experts advise against having only one Angelfish in an aquarium, as this could lead to strange behavior and your Angelfish not living long.

Suppose you want only two or three Angelfish; that is fine. You can fill the tank with other tank mates the angelfish get along with and won’t fight or eat. These would include large Tetras, Gouramis, large Rasboras, or Corydoras.

Adding To A 125-Gallon Tank To Keep The Angelfish Happy?

To ensure your angelfish are happy in their 125-gallon home, you might want to add accessories and plants they would have had in the wild.

For example, they love a hiding spot to recuperate; thus, you can add driftwood. Flowy leaf plants are also a nice touch as they love to weave through these as they swim.

Example 125-Gallon Tank Setup With Angelfish

You can opt for a sandy substrate and add lots of natural-looking accessories. Driftwood, rocks, and many live plants give Angelfish their ideal setup. Live plants you can go for are java ferns, java moss, jungle Vallisneria, and water sprite.

With eight adult Angelfish, you can add other species to fill the community tank. An example would be to add 4 German Blue Rams, 6 Juli Corydoras, 2 to 4 Neon Blue Dwarf Gourami, and 2 or 3 Bristlenose Plecos.

Other tank mates, you can consider keeping with your Angelfish:

  • Mollies
  • Platies
  • Kuhli Loaches
  • Corydoras Catfish
  • Bolivian Rams
  • Common Plecos
  • Cherry Barbs
  • Swordtails
  • Guppies
  • Keyhole Cichlids
  • Tetras
  • Siamese Algae Eater
  • Yoyo Loach
  • Malaysian Trumpet Snails

It would be best to avoid Beta fish and shrimp and any fish small enough for the Angelfish to eat. You will have to research the requirements for the fish you want to add to your 125-gallon community tank.

Ensure everyone wants the same pH levels and water temperature; this way, your schools will get along and live in harmony in your 125-gallon aquarium.


There are many debates regarding the space an Angelfish needs to flourish. In this case, more space would be better than less, so do not go less than 20 gallons for an adult-sized Angelfish. However, if you are a little tight in the area, it is okay to lower the space per fish but relocate them as soon as possible.