25 Things To Know Before Buying Discus Fish


There’s no doubt about it; discus fish are dazzling! Their bright colors and interactive behavior make them the darling centerpieces of many home freshwater aquarium. These fish are notoriously difficult to keep and even harder to breed, so we at Freshwater Central have put together this list of 25 things you should know before buying discus fish.

1. They grow up to ten inches.

When you first purchase discus fish, they will usually be around 3-4 inches or less. However, they grow very quickly in size. Fish need at least one gallon of water per inch of fish length, so be sure they have enough room to grow into their tank. You can always start out with a smaller tank, then transfer them to a larger space as they grow, but discus can become easily stressed, so it’s best to have a big enough tank to start with.

2. They need a group of their own species.

Although they sometimes fight amongst themselves, discus fish need others of their own kind to be happy and healthy. In the wild, discus feel safer from attacks when they are in a group. Even though you likely won’t have any predators in your discus tank, this behavior is ingrained in their DNA. If they don’t have safety in numbers, they will become stressed. Having a group of at least six is vital, although they prefer to be in even larger groups.

3. They need a big tank.

Discus fish need lots of room to roam. They like having their own territory where they can escape if they feel threatened. Additionally, they grow relatively large, so having ample tank space is essential. Because they need to be in groups of at least six, they should have no smaller than a 55-gallon tank. However, more room is always preferred, so having a 75 or 100+ gallon tank will keep these lovely fish happy. Happy fish means brighter colors and higher activity levels, so be sure to give them lots of space.

4. They are aggressive with some other fish.

Discus fish belong to the cichlid family. Anyone with experience keeping cichlids know that they can become quite aggressive. While each fish is different, it’s best to keep your discus away from other fish they may see as a threat, such as fish of similar size, coloration, or that occupy the same tank swim level. On the other hand, discus can harass small peaceful fish or become harassed by other, larger fish. So, be sure to carefully research any tankmates you may be thinking of adding to your discus tank before making any purchases.

5. They need vertical decorations.


Discus fish get their name from the similarity in shape they share with the discus thrown in sporting events such as the Olympics. Because of their long, thin bodies, they need decorations in their tank that they can fit through. They like to be able to hid from threats (whether real or perceived), so having vertical decorations like long pieces of driftwood or high growing plants will help them feel safe and secure.

6. They should come from a reputable source.

Discus fish are a little on the expensive side of freshwater aquarium fish, so it can be tempting to snag up those discount deals when you find them. Don’t fall into the trap! There are tons of shady fish sellers out there who want to unload stock that may be sick or have defects that will keep them from growing up healthy. Make sure to research any place that you may be considering buying discus by searching for online reviews and asking other aquarists you know.

7. They come in many color varieties.

There are few fish in the freshwater aquarium trade that can rival the multitude of color varieties of the discus fish. There is a color variety out there to suite almost any fishkeeper from camouflage browns and greens to can’t-miss-it neon pinks and purples. 

8. They have a social hierarchy.

Just like a pack of wolves will have an alpha leader, so do discus fish! The biggest and most aggressive fish is the leader, with all others following in step behind him (or her!). But this is not where the hierarchy ends. All fish in a discus school have their assigned places that they figure out by interacting with, and sometimes fighting with, each other. Like wolves, the alpha discus will have the best territory, eat the choices foods first, and have their pick of mates.

9. They need a varied diet.

You wouldn’t want to eat the same thing for breakfast, lunch, and dinner, right? The same is true with discus. While many fish species will get along happily eating the same freeze-dried flakes for every meal, the discus fish needs variety to show their best colors and activity level.

10. Their feeding schedule varies by age.


When first purchased, the discus fish you get will usually be small juveniles. Young discus grow very swiftly, so they need a lot of food to keep up with their high metabolism. However, they can only ingest small amounts of food safely at one time. Therefore, juveniles will need to be fed, usually around 6-8 times per day. When they reach their full growth, the number of feedings reduces to about 2-3 times per day.

11. You may need to feed them from multiple points in the tank.

As described above, discus have a social hierarchy, with more dominant fish tanking a leading role. Because of this, the more dominant fish may be crowding out the more submissive fish during feedings. Observe your fish while they eat to make sure everyone is getting a proper amount of food. If some seem to be getting crowded out at mealtimes and looking a little dull or sluggish, try feeding from more than one point in the tank at once. Having food enter the tank at two different ends will ensure your fish school’s docile members get appropriate nutrition.

12. They have a high bioload.

How much waste a fish produces is called its ‘bioload.’ Discus are prodigious eaters, creating a significant amount of poop. But the biggest culprit of discus fish bioload the excess mucus they shed. All fish have a layer of mucus that surrounds them to help keep their bodies protected. However, discus fish have an extra thick mucus layer that is continually shedding, requiring frequent partial water changes.

13. You may need to limit tank decor.

As described above, they need frequent water changes to remove their waste to keep it from fouling the water because of discus’ high bioload. If your discus tank is chock full of plants and decorations, these will need to be cleaned in addition to the frequent water changes. Having an abundance of decor in your discus tank will mean even more tank cleaning and maintenance, so you may want to limit decorations to cut down on work.

14. Breeding them is difficult.

Many first-time discus owners want to get into this particular hobby because they’ve heard it can be profitable to breed discus and sell the babies. While this is true, it should never be the sole motivation for a first-time discus owner because they will probably fail. Discus are challenging to breed, even for experienced discus owners. So, make sure you want them as beautiful pets first and that selling any babies would just be a side benefit. You won’t be disappointed if you end up with a tank full of non-breeding discus when approached this way.

15. Babies eat from their parents.


If you do happen to end up with discus babies, it’s essential to keep the parents in the tank with them. Lots of species of fish will eat their own eggs and even their newly hatched fry. This is true of discus too, but even if the parents start to eat their young, they have a better chance of survival if they are kept together. When discus are first hatched, they are so small that even the tiniest foods used for newborn fish are too big for them. To remedy this, discus parents grow a thickened mucus layer that is chock full of the nutrients needed for baby discus to grow. Without their parents in the tank, discus babies almost always die. With their parents in the tank, they may still die (or get eaten), but they have better survival chances.

16. They have tiny mouths.

Though they grow up to ten inches or more in size, even full-grown discus have tiny little mouths. This is important to know, so you don’t feed them foods that are too big. Discus can choke if they try to eat something too large for their mouths. If all you provide them are pieces of food too large for them, they can even starve.

17. They come from the Amazon basin.

Knowing where your fish originate (even if they are tank bred) is important to keep them happy and healthy. Fish prefer environments and water temperatures of their native lands. Because discus come from the Amazon basin, they like waters that are a little warmer than many freshwater fish, in the neighborhood of 84-86 degrees Fahrenheit.

18. They are carnivores.

Many freshwater fish are omnivorous, so they do just fine having a diet entirely comprised of those little canisters of fish flakes. Not so with the discus! When you see them serenely floating by, you’d ever guess that they are actually carnivores! Their primary food are small insects, insect larva, and worms, so make sure you make those things staples of their diet. They prefer live foods, but most will readily accept meaty frozen foods.

19. They need spotless water.

Your discus must live in water that is clean and well maintained. As mentioned above, this can be a challenge due to their relatively high bioload. Frequent partial water changes and an excellent filtration system is a must to keep the water in your discus aquarium in pristine condition.

20. They can live up to ten years.


Before committing to discus fish, know that they can live up to ten years. This is no small time commitment, so be sure you’re ready to take care of these fish for the next decade.

21. They get spooked easily.

As said before, discus fish have many predators in the wild, so their instincts are wary of any perceived threat. Therefore, it’s essential to keep your discus tank away from highly trafficked or noisy areas of your home. Having lots of shadows pass by their tank will make them nervous and they will hide. Loud or sudden noises can also send them into a panic. So, keeping them away from boisterous pets, active children, and your sound systems are a must in keeping them feeling safe and secure.  

22. They are sensitive to bright light.

As described above, fish like to be in tank environments that mimic their home territories. Because the Amazon basin from which they come is not a particularly well-lit home, discus may hide from bright lights. This doesn’t mean you have to forgo all aquarium lights. Just make sure they have some covered spots, such as patches of floating plants or decorations, where they can catch some shade if things get too bright. Additionally, make sure to turn the lights off at night so they can have some well-earned rest from the artificial sun.

23. They are interactive with their owners.

One of the many reasons discus fish are so fun to own is that they will often recognize their owners and interact with them. They can tell basic things from the people that come up to their glass, so if you are the primary owner (the person who feeds them most often), they will come to associate you with food and swim eagerly up to the glass when you approach. This is truly endearing behavior that is just one of the few reasons that discus owners become so attached to them as pets.

24. You can feed them by hand.

Because they interact with their owners and often associate them with food, you can feed them right out of your hands! Pick their favorite live or frozen meaty food and hold a pinch of it in the water. Discus who know their owner will come right up and eat from your fingers.

25. Sand is the best substrate.

Discus love to forage along the substrate to scoop up the food they miss during feeding times. Because of this and the fact that they have delicate fins, a soft, fine-grained substrate is best for them. Sand is preferred to fine gravel, although anything small and smooth enough is suitable. 


Discus fish are, no doubt, some of the most beautiful aquarium fish in the world. However, they can be challenging to care for, especially for beginners. If you’ve read through this list and decided that you want to try your hand at keeping these stunning animals, be sure to check out our guide on how to build your dream discus aquarium.

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