How Many Discus Fish in 3, 10, 15, 20, 25, or 30-Gallon Tanks?

Discus fish is a little hard to handle as compared to other aquarium fish. Before purchasing this majestic beauty, you’d want to make sure that they get a perfect tank size and an ideal environment.

How many discus fish can you keep in your tank? To keep the discus fish in ideal conditions, a large-sized tank is preferable. One fish per 10 gallons of water would work fine for discus. Since these fish like to live in a group of 5-6 discus, you would have to provide them at least 50 gallons of water.

In this article, we’ll talk about different tank sizes for discus fish according to the fish’s life style, behavior and requirements.

Tank size

You have to figure out the ideal tank size according to the number of discus fish to provide them with the proper environment to thrive.

Discus needs a larger tank to survive as compared to other aquarium fish. A deep and big tank is recommended for a discus to sustain a happy life.

Let’s find out the capacity of different tanks for the accommodation of discus fish:

3-gallon tank

As mentioned earlier, the discus fish needs a wide tank to move around and live joyfully with other tank mates. But 3 gallon is just a size of a fish bowl which is not suitable for keeping discus. Even if you want to keep a single fish in that size, it is not recommended.

If you think you can keep a discus fry in a 3-gallon tank, then it is also not possible as discus fry need to stay with the parents during the first few weeks after they are born.

10-gallon tank

A 10-gallon tank is suitable for keeping a single discus fish. To create an ideal atmosphere inside the tank, you also need to install plants or accessories which take up a lot of space. This makes a 10-gallon tank unsuitable for discus fish. If you will keep more than one discus, that tank space would be insufficient for both of them.

It is important to note that discus fish like staying in a group of 5-6 and it is not recommended to keep them isolated in a tank.

15-gallon tank

A 15-gallon tank is a small space for a pair of adult discus fish. You can keep 2 discus fish in this size but they won’t live happily or for a long time.  However, you can keep 2 baby discus fish when they are not fully grown inside a 15-gallon tank. For healthy growth of discus fry, get the tank water cleaned regularly or install a high-quality filter. But as soon as they grow large, you would have to upgrade the tank size or shift one fish to a separate tank.

20-gallon tank

Inside a 20-gallon tank, you can easily keep 2 discus fish including tank accessories. This will be the ideal tank size for a pair of fish to live and carry on their daily activities. If you are keeping a male and female together, then get ready to welcome their babies if they end up mating.

For the first few weeks, you can keep the fry along with parents but eventually you will have to move them in a separate tank to avoid the overcrowding. Discus fish fry also start harming their parents after a few weeks so separating them into another tank is the right option for you.

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25-gallon tank

A 25-gallon tank can accommodate 2-3 discus fish easily. Keeping in mind the presence of aquarium plants, you are suggested not to add excessive items for decoration. Without too much accessories, a 25-gallon tank might be able to provide sufficient space for 3 discus to swim around.

30-gallon tank

A 30-gallon tank size is ideal for 3 discus fish. You can keep them, breed them and care for them in the best manner by cleaning their tank regularly. If you increase the number of discus in your tank, then they might survive but it won’t be an ideal condition.

Cramping your discus fish in smaller spaces will lead to stress and various diseases.

50-gallon tank

Inside a 50-gallon tank, you can keep almost 5-6 discus fish together. It is easier to create an ideal environment for that number in such a wide space. Install plants, spawning surfaces, and an electric filter to maintain the water conditions.

If you want to mix fish from any other breed with discus, then you should minimize the number of discus to 3 in this tank and add 2 other fish. Do not forget to check if the other fish are compatible with discus, otherwise, they would end up fighting and harming each other.

This is the most recommended tank size to keep discus fish. In this tank, they will delightfully live together in the form of group. Any tank smaller than the 50-gallon size is not a good choice to keep the discus fish.

100-gallon tank

A 100-gallon tank makes for quite a large aquarium. But if one wants to create a community tank with other fish breeds and lots of tank decor, then 100-gallon is the ideal, and if I may, premium size. But even with this size, you should always understand your limitation and avoid overcrowding. Limit the number of discus to 10-11 in this tank.

If you add more than 11 discus, then the tank will become overcrowded and hard to maintain. If you spot a breeding pair inside this community tank, consider moving it to a separate tank until the fry are born.

Other tank conditions

The internal conditions of a tank which require your attention are the following:

  • Tank décor
  • Tank position
  • Tank maintenance

Tank décor

Discus fish enjoy living in a colorful environment. You can decorate the inside of the tank with driftwood, plants, and rocks to mimic the natural habitat of the fish.

Also, keep in mind that you don’t overcrowd the tank with these accessories otherwise they will consume too much of the swimming-space of the discus.

Tank position

The tank placement also requires your consideration. Discus is shy by nature, so their tank should be placed at a peaceful and quiet place. The place must be dark, noise-free, and away from direct sunlight or heat.

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Discus fish tank conditions

Discus fish is highly sensitive towards the tank conditions so you have to pay extra attention to keep them ideal for your fish. They require certain water conditions that might be hard for an amateur aquarist to maintain. Due to the lack of care and unsuitable conditions, these fish die easily.

The well-being of your fish highly depends upon the quality of the water. They prefer soft, warm, and acidic water. The water temperature should be between 82°F and 86° F. The pH of water must be between 6.0 to 7.0 and hardness of 1°-4° dKH.

You should keep an emphasis on keeping the water clean and dirt free. Avoid changing the tank conditions frequently because it can lead the fish towards stress. If you fail to keep the water clean then your fish will get sick and eventually lose their lives.

Tank maintenance

To ensure that your aquarium is in the best condition for the growth of discus, follow the given instructions:

  • Regular change of water on a weekly basis.
  • Placement of tank at a quiet place
  • Isolate sick fish to protect others from getting an infection
  • Feeding them in small batches daily
  • Maintaining the temperature and pH of the tank water
  • Installing a high-quality filter for eliminating toxic materials from tank water


Which of the other breeds of fish are compatible with discus fish? The species of fish which can adjust under same tank conditions as discus are suitable tank-mates for them. These ideal tank mates include characins, dwarf cichlids, pearl gouramis, neons, emperors and corydoras. Do not add the fish which are bigger in size than discus.

What should I feed my discus fish? In wild, these fish eat plants, live worms or crustaceans. In an aquarium, you can feed them flakes, algae, frozen worms, bird shrimps etc. Beef heart is favorite food of discus fish. For the fry discus, you can get liquid food or give them egg yolk in powdered form. For the best outcome, feed your adult fish thrice a day and give them limited food which they can eat in 5 minutes. Overfeeding can be harmful and lead them to death. Also, do not leave the left-over food inside the aquarium as it can decay and increase the toxicity of water.

What is the growing rate of discus fish? A newborn fry is almost 2 inches long and it can grow up to 6-8 inches in length until they reach adulthood. They increase in size at the rate of 0.5-1 inch per month. A pet discus fish is fully grown at the age of 2-2.5 years. If they are kept under optimum tank conditions with healthy food, they can live for 10-15 years.

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Nadine Oraby

My name is Nadine; I am a passionate writer and a pet lover. People usually call me by the nickname “Joy” because they think that I am a positive and joyful person who is a child at heart. My love for animals triggered me to create this blog. Articles are written by vets, pet experts, and me. Thanks for visiting. Your friend, Nadine!

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