What to Know About Discus Fish

Reviewed by Vanesa Farmer, DVM on December 10, 2022

You’re considering new fish for your home aquarium, but all you see in your local pet store are the usual guppies, tetras, and small cichlids. You want a more unusual fish that stands out from the others. The discus may be the right fish for you. Discus fish are disc-shaped, brightly colored specimens that originate in the tropical waters of South America. 

Discus fish, like other cichlids, are often difficult for beginners due to their strict water parameter requirements. Learn more about the discus and understand the finer points of its care with the help of the following guide.

All discus are members of the Cichlidae, or cichlid, family. There are over 1,000 species of these freshwater fish in the wild, and many smaller types are kept as pets in home aquariums. You might see blood-red parrot cichlids, Oscars, angelfish, and discus fish in your local pet store. Some cichlids, like tilapia, are regularly consumed as a part of the human diet. Others in this family of fish are classified as endangered. 

Cichlids’ appearances vary widely. Some are huge, and some are tiny. Some are colorful, and others are stone-gray. You can easily pick out a discus by identifying the following traits.

Color. Discus fish are often categorized as blue, red, and green species. The names are a bit misleading because the “blue” type also includes brownish fish, and the green fish are more yellow than green. The red species is typically the brightest of the discus group.

Size. Don’t be fooled if you see a small juvenile discus in a pet store. The fully grown discus size ranges from 5 to 9 inches in diameter. Because they prefer to swim together, you should take into account their large mature size when purchasing multiple discus fish. Experts recommend keeping discus in a 55-gallon tank at minimum.

Personality. Discus are peaceful fish that are rarely aggressive. When considering tankmates, look for other discus (which they will be most happy with) or other cichlids that require the same water parameters and have a similar laid-back personality.

Cichlids can be high-maintenance pets. If you’re up for a challenge, memorize the following points to ensure a healthy habitat for your new discus.

In the wild. Because discus fish are native to the Amazon area in South America, they prefer water that’s on the warmer side — even for tropical fish. In their native habitat, they swim in Amazon tributaries that range from around 80°F to 95°F. 

Discus are often found in “black” water areas in the wild. These waters aren’t actually black, but they are quite dark due to the acidic content of the water that develops as a waste byproduct. They enjoy living in groups — it’s possible to find up to hundreds of discus swimming together if there’s enough room in the area — and they prefer to dwell under tree roots and shrubbery on the banks of these streams and rivers.

In your home aquarium. Your fish tank at home should closely resemble the natural habitat of the discus. It's important to have a big enough tank to host the fish, plants, and substrate (the rocks or sand you choose to line the bottom of the tank). 

The general rule of thumb is to stock your tank with 1 inch of fish per 1 gallon of water. You should also keep in mind that, as a social fish, your discus needs companions. Consider the following care tips when setting up your discus habitat or when thinking about adding a discus to an established tank:

  • You should select tankmates that are compatible with the discus. For example, you shouldn’t keep a goldfish and a discus together, regardless of their peaceful temperaments, because a goldfish prefers much colder water than a discus.
  • The pH level of your water should reflect that of a discus habitat in the wild. These fish prefer soft, acidic water with a pH of around 7 or higher. The “general hardness,” or GH, of your tank should be 3 to 14 degrees of GH. There’s a bit more wiggle room with the water hardness than there is with the pH. Try to keep your water parameters the same, without drastic deviations, as your discus may suffer with large changes. Don't try to change your pH or water hardness quickly, or you could harm your fish.

Not all tropical fish eat flakes. Some eat pellets, some eat cooked vegetables, and some eat small crustaceans like brine shrimp. Feeding your fish food that isn’t right for them can cause a nutrient deficiency and lead to a shorter discus lifespan and poor health overall.

Discus fish thrive on an omnivorous diet. In the wild, they eat algae, plants, insect larvae, bugs, plankton, and whatever other tiny creatures they can fit in their mouths. In captivity, they need a variety of nutrients and protein to stay healthy. To meet your fish’s nutritional needs, try feeding it a variety of live or freeze-dried food like bloodworms, mosquito larvae, and commercial food formulated specifically for discus species or cichlids.

Some fish, like guppies, are livebearers — meaning that they will have live babies that don't hatch from eggs. But discus females lay eggs that are fertilized by the male discus fish. 

When the eggs hatch, the parents take care of them by protecting them from predators in the wild. The baby discus fish will eat the mucus secreted by their parents’ skin until they are old enough to eat a regular diet. If you’re considering breeding your discus in captivity, follow these guidelines:

  • Select a breeding pair after you’ve seen them exhibit mating behavior.
  • Consider moving the breeding pair to a separate clean tank or away from other fish that might eat their young.
  • Keep the pH in the “baby tank” slightly lower — around 5 to 6.5 — to ensure the health of the young discus fish.
  • Feed the discus babies a similar diet to that of their parents when they're finished eating the parents' mucus secretions. 

Keeping discus can be nerve-racking if you’re not used to maintaining strict water parameters and performing frequent water changes, but it can be well worth the effort. Speak to a veterinarian who specializes in fishkeeping if you have more specific questions about daily discus care, illnesses that affect your fish, and more.

Show Sources

Animals Network: “Discus.”
Caring Pets: “11 Factors of Goldfish Aquarium Water Quality.”
It’s Not Just a Fish: “Do fish grow to the size of their tank?” “Understanding fish stocking guidelines.”
North American Discus Association: “Is My Water Too Hard for Discus?”
Royal Society for the Prevention of Cruelty to Animals: “What to feed your pet fish.”
San Diego Zoo Wildlife Alliance: “Cichlid.”
University of Florida, Institute of Food and Agricultural Sciences: “Candidate Species for Florida Aquaculture: Discus Symphysodon spp., A Profitable but Challenging Species for Florida Aquaculture.”

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