10 Common Discus Fish Owner Mistakes


Discus fish are notorious both for their beauty and for their difficulty in keeping. While they require more attention than average tropical fish, their stunning colors make them one of the most beautiful freshwater fish in the hobby. Novices and experts alike can fall victim to mistakes, so read on to give you the knowledge to avoid these ten common Discus owner mistakes. Want more information? Check out our complete Discus fish care guide!

  1. Diet variety

Some of the most common mistakes made by Discus owners regard feeding. The first of which is not keeping enough variety in their diet. In the wild, Discus fish are omnivores, so they need a mixture of both plant-based and meaty foods. Keeping a ratio of at most ⅓ meaty foods and at least ⅔ plant-based foods will ensure your Discus get the protein, vitamins, and minerals that they need to be healthy and show their best colors and activity levels. 

High-quality flake and pellet food that is specially designed for Discus should be their primary source of food. But, since they eat small worms and crustaceans in the wild, they should also be fed these in sparing portions. Frozen brine shrimp, blackworms, and blood worms are good options for meaty foods. While live foods are possibly the favorite food of Discus, special care should be taken if you use this option. Live foods can carry parasites, diseases, and other foreign bodies into your tank. They can also camp out in your tank by hiding in decorations, or die and become lost in plants and substrate. So, if you choose to give your Discus live foods, keep a careful eye on the tank, and frequently check your water parameters.

Another problem that arises from not giving your Discus a varied diet is they may become finicky eaters. If you give them the same food repeatedly over a long period, they will favor that food and reject others. This will deprive your Discus of critical nutrients. Also, uneaten food will foul your tank water quickly. If your Discus have become selective in their feeding habits, it will most likely be in favor of protein-rich foods. To break this habit, for their first feeding of the day, use only foods with quality, plant-based ingredients. Since they are generally hungrier first thing in the morning, they will be more eager to accept foods that are not their favorite. Then, gradually increase the amount of plant-based foods in the rest of their feedings.

  1. Food size

When Discus are full-grown, their impressive 8 to 10-inch size may lead you to believe that they have proportionally sized mouths. In reality, their mouths are bigger than their throats, even as adults. While adults will be able to handle pieces that are a little larger, the throats of juveniles are nearly minuscule. While it’s common for Discus to eat a piece of food and spit it out a time or two before swallowing, if you see your fish repeatedly eating and spitting out food, it is a sure sign that you’ve given them pieces that are too big. 

For juvenile Discus, start with tiny pellet food to measure for size. If this is too big, grind up flake food, mix with a small amount of water, form this into small balls and release it into the tank. Another good way to measure for size is to add little bits of frozen food to the tank, as it will dissipate in the water as the fish eat. If you’re still having trouble with feeding juvenile Discus, you can always give them baby brine shrimp until they are a little bigger. As the Discus age, you can gradually increase the size of their food.

  1. Over or Underfeeding
Discus feeding

It is very easy to overfeed aquarium inhabitants, and Discus fish are no different. Discus are particularly tricky as they require feedings multiple times per day. Fry need to be fed up to twelve times per day. Juveniles require up to five feedings per day. Once your Discus are full-grown, at twelve months of age, you can reduce giving food to two to three times per day. 

For each feeding, only feed them what they can eat in approximately five minutes. Discus like to scavenge the bottom of the tank for leftovers. It is perfectly acceptable to let them do this for up to an hour after feeding time. However, make sure to keep an eye on the time and remove any leftover food after an hour to prevent overfeeding and water pollution.

To make things even more complicated, underfeeding can be just as big of a problem for your Discus fish as overfeeding. Underfeeding in the three to twelve month age range can cause stunted growth and deformities. Underfeeding at any age can cause starvation, which will cause your Discus to behave unusually. If it goes on for too long, underfeeding can cause your fish to die. 

Overfeeding and underfeeding can also happen even if you give your Discus the proper amount of food. Because they develop a social hierarchy, the more dominant fish can crowd out more submissive individuals. Pay close attention to how much food each fish is getting. If it seems a few are getting pushed around, try offering two feeding places in the tank at the same time. This way, the dominant and submissive fish can each have their own food source.

  1. Too much decor

Most aquarists love the look of a beautifully decorated aquarium, whether stocked with dense leafy greens or colorful artificial castles. But with Discus, because they need a considerable amount of attention to begin with, having a lot of decor will just increase your amount of work. If your dream Discus aquarium includes a lot of decoration, make sure you keep things to a tasteful minimum if you want to avoid creating extra work for yourself. As any aquarist knows, cleaning plants and decorations is a time-consuming task.

  1. Tankmates

Many aquarists, myself included, love a community tank with lots of colors, different energy levels, and animals that like to hang out in different areas of the tank. But Discus fish are very particular about their tank mates. The best option for them is a species only tank, but Discus do not do well when kept on their own. Just like wolves, Discus are happiest when they are in a ‘pack’ or group. When establishing a new tank, or adding new fish to an established Discus tank, they will need to determine who is the leader of the pack, the leader’s right-hand man, the leading lady, and so forth. This is typical Discus behavior, so don’t be concerned if your new Discus are fighting. They will calm down quickly. The only other time you should see dominant/submissive behavior is during feeding time. While this is normal, take care to ensure that all fish are receiving the sustenance they need. 

If you just can’t handle a tank with only one species, some fish get along well with Discus. Keep in mind their preference for higher temperatures and soft, acidic water when looking for tank mates. One of the most popular choices for Discus tank mates are Corydoras. Corydoras, also known as Cory’s or Cory Catfish, are peaceful, bottom-dwelling fish. Since they aren’t similar in size, shape, or color and occupy a different swim level than Discus, they leave each other well alone.

Hatch Fish are also good options for the same reasons as Cory Catfish, as they are peaceful and occupy different tank levels. Cardinal Tetras thrive in the same water conditions as Discus and will have no problem if kept in a large group. Just be sure to have a planted tank with Cardinals, so they feel safe from the larger Discus. Many experienced aquarists have also had good luck keeping their Discus with Neon Tetras, Rummy Nose Tetras, Dwarf Cichlids, and Plecos.

  1. Understocking

It’s essential to research the amount of Discus you should have for your tank size. For example, keeping only three Discus in a 55-gallon tank, either with a community or species only tank, will quickly lead to problems. With too few specimens, the natural aggression of Discus fish will be more prominent. The dominant fish will pick on the others, and the submissive fish will have few options to escape. Even with other tankmates, if you have too few Discus, the submissive ones will become targets and be subject to harassment to the point of death.

The same is true, even in a community setting. Discus need other Discus to display their best colors and remain happy and healthy. If you only have one Discus in a community of several species, they will become shy, withdrawn, and depressed. Even though they maintain a pecking order where some fish are deemed to be more important to the group, even the most dominant Discus needs subordinates of their kind to be fulfilled. 

  1. Overstocking

There is equal danger in overstocking your Discus tank. No matter if you keep too many individuals in a species only tank, or have too many fish in a community tank, overstocking is a sure ticket to unhappy fish all around. Overstocking is a particular problem with Discus because there is such a big difference in their size between juveniles and adults. While ten to fifteen young Discus are fine in a 55-gallon tank, they will quickly outgrow it and become unhappy at the cramped conditions. Discus are sold as juveniles when they first reach about three to four inches in length. This pales in comparison to their impressive eight to ten-inch adult size. Because of this, the same number of Discus that are quite happy in smaller tanks will fast come to despise their home. It’s always better to overestimate the amount of space you will need for any kind of full-grown fish. So, err on the side of caution when calculating the size of the aquarium you will need and the number of Discus you should purchase.

  1. Improper Substrate

While there isn’t any particular substrate that is “wrong” for Discus, some are better than others. You want to avoid anything with sharp edges, as Discus fish like to forage along the bottom of the tank and suck up stray pieces of food or things that might be stray pieces of food. They can easily be injured by trying to ingest small pieces of sharp substrate or scratching their bodies against it. 

An equally avoidable substrate is large-grained gravel or pebbles. Fish waste and leftover food can easily fall between the cracks and pollute water quality. If you go with an option like this, you’ll have to vacuum the gravel of a 55+ gallon tank every day or two to keep things tidy. So, prepare to roll up your sleeves for regular, time-consuming work.

The best option for the bottom of your tank is to either use sand or leave it bare. Even larger grained sand, such as the pool filter variety, is small enough that any waste or leftover food will be easily visible sitting on top of it. A quick clean up during your regular water changes is enough to keep sand or bare bottom tanks neat and tidy.

  1. Poor Water Quality
water quality

Having poor water quality will lead to inevitable failure for any Discus tank. They can handle a moderate range of temperatures, acidity, and hardness, but steadiness is the key to success. Because they have a high bioload and shed mucus-like crazy, even in a species only tank, the water quality can change drastically from day to day. It’s common for Discus owners to think that they will be similar to more adaptable tropical species that only need a 25% water change once per week. In a large, bare tank, you might be able to get away with this, but likely not. Even if this is the case, you should still monitor your water parameters at least a few times per week and keep a close eye out for any strange behavior in your fish.

  1. Taking bad advice

Advice and opinions on the proper care and maintenance for Discus fish are everywhere on the internet. Make sure your information comes from reliable resources. Ask questions from Discus owners. Don’t know any? Look up forums and message boards for aquarists or specifically for Discus keeping questions. If you’re looking for websites, make sure they are active and post regular content. The longer the site has been around, the better, so check the date on some of their other posts to make sure some are at least a few years old.


We hope this list of common mistakes among Discus owners has been helpful for you and your fish! Discus require a lot of work, but they are so gorgeous they remain a prevelant species for freshwater aquariums. Key rules of thumb are to do lots of research, keep your tank super clean, vary their diet, and have the proper number of Discus, tankmates, and size of the tank. Please let us know any questions or comments below!

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