10 Most Common Beginner Discus Fish Mistakes


Discus fish (also called just discus) are stunning fish that are sure to be a centerpiece of your home. They have fascinating personalities and make wonderful pets. However, keeping discus fish is not an easy task, even for experienced aquarists. But don’t let that stop you! Every discus keeper has to start somewhere. Just make sure to not fall victim to one of the following top 10 most common beginner discus keeping mistakes.

1. Not Researching your Seller

One of the first things you’ll do when starting a discus tank is deciding the fish you may want to purchase. There is a vast array of discus varieties that come in numerous colors and patterns. Once you have your tank set up and cycled and your chosen type picked out, it’s time to start shopping! 

There are tons of places to buy your fish, but you should take care to research sellers before taking the plunge. Some will offer stock that is less healthy or colorful at a lower price. Others may be just starting in the discus selling trade and not have sufficient knowledge on how to care for them. 

Any reputable seller should have reviews and a history in the fish trade that is easy to find online or through word of mouth among other discus keepers. Make sure to look at the seller’s reputation, not just their price, when deciding where to purchase your fish.

2. Mixing Tankmates


While you may see gorgeous discus tanks full of multiple species, beginners should stick to just discus in their first tank. These fish are very territorial, even among their own kind. Having lots of other fish in the tank to compete with can make them overly aggressive or uncomfortable, which leads to fighting amongst your fish. It’s not that you can never have other kinds of fish in your discus tank, but it is a good idea for beginners to start with a species only tank. Once you have some experience under your belt and know how to care for discus on their own properly, you can start experimenting with adding other species.

3. Too Much Decor

Discus fish make a lot of waste, which is also known as having a high bioload. When fish have a high bioload, you have to do water changes and clean the tank and decorations more frequently. As we will discuss in the next step, discus fish need to have pristine water conditions, so you will already have to be doing water changes at least once per week. If you have a ton of decorations, this will add significant time to your weekly maintenance routine.

Additionally, substrate is something you should either skip or keep to a minimum in your first discus tank. Having a  high bioload means that lots of waste and uneaten food will accumulate at the tank’s bottom. Keeping a bare bottom of your discus aquarium will help you better see when the tank needs cleaned and allow you to remove any uneaten food between feedings easily.

Additionally, it will remove the added step of having to vacuum the gravel or substrate. When uneaten food and fish waste sits at the bottom of the tank and sinks into the space between gravel pieces, it will foul the water and create a bacteria breeding ground. Discus fish are very sensitive to water quality, so keeping your substrate and decorations to a minimum will help ensure they stay healthy. You can read more about caring for your discus fish here.

4. Infrequent Water Changes

As stated above, discus fish need excellent water quality to remain healthy and show their best colors. As the fish go about living their lives (and when you clean the tank), particulate matter gets mixed in with the water. This can alter the water chemistry, which is bad news for your fish. To combat unhealthy water conditions, you need to do partial water changes.

Because discus have such a high bioload, you will need to do these changes more frequently than you would with many other species. We recommend that you do approximately 25-30% water changes once per week. Failing to do so can make your fish unhappy and unhealthy.

5. Adding Fish at Different Times


Experts often suggest with many species that you buy a few fish, give them some time to check out the tank and feel comfortable, and then add more fish later. With discus fish, this can be a huge mistake! Discus form complex social hierarchies. Adding new fish to the group once their roles have been established can cause fighting between individuals. It can also lead to a group of fish ganging up on the newcomers and harassing them to death.

To avoid this, choose a large tank and, once it’s cycled, add your fish in a single day. You should have at least ten fish, but more is preferred depending on your tank size. This helps spread out the fish’s aggression so that no individual is singled out as a target to get picked on.

It’s also a good idea to purchase discus that are all the same approximate age and size. This will help keep younger fish from being targeted. For example, if you buy ten juvenile discus, then add ten more juveniles in a few months, the older fish may start fighting with the younger fish to defend their established pecking order. Discus fish grow rapidly when young, so even an age difference of just a month or two will result in a disparity of size.

6. Improper Tank Size or Shape

Discus fish are named for their round, thin body shape, similar to the disk thrown by Olympic athletes in the discus event. Their profile is quite unique in the freshwater trade, so they require a specific type of tank. 

They have very slender bodies but are quite tall, so they need a tall enough tank to fit their frame. They also grow more extensively than many freshwater fish (six inches long and eight inches high), so they need plenty of space to stretch their fins. A group of five discus will need a minimum tank size of 55 gallons. 

However, discus fish are happiest when they are in groups of at least 8-10. Additionally, having more than just the minimum amount of space will make them more comfortable and make things easier for you, the keeper. When they have more than enough room, it gives individuals who are lower in the social order more places to escape if they are drawing aggression, which increases their lifespan and level of comfort. Happy fish show better coloration and activity level than unhappy fish, so make sure your first discus tank has plenty of room to spare!

7. Feeding the Wrong Amount


Discus are known as fussy eaters, especially when they are juveniles. This can be a huge problem when they’re first introduced to a new tank. If your new fish don’t eat, they will quickly starve to death. Discus are so picky that even if they are on death’s door, they won’t eat what you put in front of them if it isn’t the right kind of food. The same holds true if the food isn’t the correct size.

A varied diet and controlling the amount your discus eat is vital to their long-term health. Discus are omnivorous, so you should feed them a mix of both plant and meat-based foods. They have small mouths, so make sure to break up their food to an appropriate size. If your discus aren’t eating the foods you provide, try offering them quality live or frozen foods, such as baby brine shrimp, bloodworms, or white worms.

It is also a good practice to closely observe your discus at feeding time. Because of their social hierarchy, dominant fish may crowd out submissive fish at mealtimes and steal all the food! If you notice your submissive fish aren’t getting enough food, you may want to put food at each end of the tank at once. This way, the fish getting pushed out by the alpha fish will have their own place to feed.

8. Under and Overstocking

Discus are social creatures. Even though they may fight with each other for dominance and mates, they still need to be kept in groups. A lone discus will quickly become stressed out or depressed, leading to illness, low color and activity levels, and even death. They need others of their own species in order to define the way they interact with their surroundings. 

Depending on your tank size, you should have a bare minimum of five discus fish. However, groups of at least ten are a better option for beginners. While your discus may survive if you understock them (keeping too few), they almost certainly won’t if you overstock (keeping too many). When discus don’t have enough space, they will fight each other to the death to make more room for themselves.

9. Skimping on Hardware

There’s no way around it; keeping discus is an expensive hobby. They need lots of space relative to their size, which means a big tank and lots of equipment. If you’re trying to save money, it may be tempting to buy cheap equipment and skip a few things you don’t think you need. This is a huge mistake!

Discus need exceptionally clean water, so be sure to invest in a filtration system that can handle the workload. While inexpensive doesn’t necessarily mean something is bad, it can signify it’s made with low-quality materials that will need to be replaced. Make sure to choose a quality filtration system that has many positive reviews.

In addition to buying quality equipment, be sure you don’t skip buying anything your discus fish will need. For example, many people who keep freshwater fish will omit a heater from their aquarium set up. Many of these fish can tolerate room temperature water just fine, so it isn’t a big deal for those types of aquariums. But discus fish are different. They thrive in warmer tropical waters above 80 degrees, so having a heater for them is a must. Additionally, they are sensitive to changes in water temperature. Adding a heater to the tank will help keep the temperature stable. Find more information about building a discus aquarium on our guide.

10. Bad Tank Placement


Picking the perfect place for your tank is more than just an aesthetic choice. Where you put your tank will also affect your discus fish’s health and happiness! Discus are very interactive fish. They take a great interest in what is happening outside the tank. They will regularly follow you around the tank and respond to changes in light, sound, and activity levels. This is just one reason why they make such fascinating pets. But, it is also a reason you need to choose the tank placement with care.

Putting your tank in a high traffic area can cause your discus to become stressed. Having strange shapes and shadows pass over their tank continuously throughout the day will make them feel threatened and cause stress. Stressed discus will hide, become dull in color, and may stop eating. So, be sure to put your discus tank in a tranquil location in your home away from high traffic areas or where people regularly congregate.

Tank placement can also affect the temperature of your aquarium. Make sure to place your tank in a place that is well away from windows and air vents. Bright light and cold weather are two things that can alter the temperature in your tank, so keep it away from windows. Air vents that pump hot and cold air into our homes to make us more comfortable will make your discus less comfortable. So, make sure your tank is far away from air vents as well.


Every experienced discus owner has started just where you are now – as a beginner! Keeping discus fish is a challenge, but well worth it due to their unique personalities and stunning colors. There are several things about owning discus that may be difficult, but with study and persistence, you will have a thriving tank in no time! Be sure to check out our guide if you’d like more information on common discus mistakes.

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