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How Big Do Discus Fish Get?

Are you wondering how large discus fish can get? Well, this aquarium fish can grow to be pretty big! The average size for a discus fish is around 7 inches, but discus fry can grow up to 9 inches. So, if you’re looking for a big discus fish, then the discus fish is a good choice for other tank mates.

However, this is dependent on how many discus fish eat and the quality of their environment. As long as you provide them with a good diet and a clean tank, then the discus fry should be able to reach their full potential.

In this article, I’ll share everything you should know about the size of discus fish. I’ll also give you some tips on how to ensure that your discus fish grow to be healthy and large.

How Large Can Discus Fish Get?

In the wild, discus fish can grow to be around 4.8–6.0 in (12.3–15.2 cm). However, in captivity, discus fry typically only grow to be around 9 inches (23 cm).

This is due to the harsh conditions they encounter in the wild. They don’t have access to the same quality of food or water, so discus fry don’t grow as large.

In captive environments, discus fish receive high-quality food and live in tanks with excellent water conditions. This allows them to reach their full potential size-wise.

How Long Does It Take for Discus to Grow?

Discus fish grow relatively quickly. They can reach their full size in just 2 to 2.5 years. However, their growth slows down to a crawl once they reach 4 or 5 inches. This slowdown continues until the discus fry reaches 6 or 7 inches in size.

The table below shows the average growth rates for discus fish:

5 cm2 months2”
6 cm3 months2.5”
8 cm4 months3”
10 cm6 months4”
12 cm9 months4.5”
14 cm12 months5.5”
15 cm18 months6”
17 cm24 months6.5”

How to Make My Discus Fish Grow Bigger?

Provide Them with a Small Tank

When caring for baby discus fish, you should start them off in a small tank. This will save their energy for growth instead of swimming around a large tank.

Also, small tanks are easy to maintain when your discus fish are still young. You won’t need to do huge water changes as often, and you can keep a closer eye on your discus fish.

As they are adult discus fish, you can gradually increase the size of their tank. A 10-gallon tank is a good size for an adult discus fish.

Adjust Proper Water Temperature

Can you withstand extreme heat or cold? No, and your discus fish can’t either. That’s why it’s important to adjust the water temperature to their needs.

Discus fish prefer water that is between 82–86 °F (28–31 °C). In case you didn’t know, that’s pretty warm!

To maintain this temperature, you can use an aquarium heater with a temperature regulator. This will help you keep the water at a consistent temperature.

Give Them a Well-Balanced Diet

Just like every other living creature, discus fish need a well-balanced diet to survive. A good diet will help them grow to their full potential size.

Since these guys are omnivores, they’ll need both aquarium plants and meat in their diet. You should give them a varied diet that includes:

  • Frozen or live foods such as bloodworms, daphnia, brine shrimp, and earthworms
  • Vegetables and Aquarium plants such as blanched zucchini, cabbage, and spinach
  • High-quality discus food pellets or flakes

Overall, you should avoid giving your discus fish too much food. A good rule of thumb is to only feed them what they can eat in 2 minutes.

If you overfeed them, then the leftover food will sink to the bottom of the tank and decay. This will raise the ammonia levels in the water and put your discus fish at risk for disease.

Perform Regular Water Changes

Discus are pretty robust fish, but they’re still sensitive to ammonia and nitrites. That’s why you need to perform regular water changes to keep the water clean.

As a general guide, change 30% of the water every day. If that’s not possible, you should do a 50% water change every two days at least.

To make sure your discus fish are always safe, you should have a water testing kit. I recommend the API Freshwater fish Master Test Kit.

Also, don’t forget to add a water conditioner to the new water to eliminate any hazardous chemicals and make it safe for your fish. This way your buddies will enjoy an appropriate environment that facilitates growth.

Maintain Right pH Level

In my opinion, the pH level is one of the most important water parameters for discus fish. These freshwater fish prefer water that has a pH level between 6.0 and 7.8.

If the pH level falls outside of this range, it can cause serious health problems for your fish, thus affecting their growth.

To maintain the right pH level, you should use a pH testing kit to check it regularly. If the pH level is too low or high, you can use a pH adjuster to fix it. I recommend using Seachem Prime because it’s safe and easy to use.

Provide Ideal Group Size

Discus babies won’t establish a pecking order if they live in a group of ten or more. Pecking order is a social hierarchy where each fish has a specific place in the group.

As a result, the stronger or more aggressive fish will constantly bully the weaker ones. This will cause stress, which can lead to disease and affect their growth.

However, if you provide the ideal group size, each fish will get an equal share of food and attention without any bullying.

Why Isn’t My Discus Fish Growing Fast?

Poor Genetics

Unfortunately, some discus fish are just born with poor genetics and will never reach their full potential size.

There’s not much you can do about this except return them to the store or breeder and get a refund! Therefore, when buying discus fish, make sure to buy them from a reputable source.

Low Protein Diet

I know the feeling. You want to save money on fish food, so you feed your discus fish a low protein diet.

While this might save you some money in the short term, it will actually stunt their growth in the long run. That’s because protein is essential for proper growth and development.

To make sure your fish are getting enough protein, feed them a diet that’s high in quality and includes lots of live, frozen, or freeze-dried foods.

Too Much Ammonia Build Up

Can you imagine yourself living in a house with no toilet? How long do you think you would last before the ammonia buildup made you sick?

Discus fish are the same way. If there’s too much ammonia in their tank, it will make them sick and affect their growth.

Also, ammonia spikes encourage bacteria, algae, and fungi to grow. These can harm your fish and make it harder for them to breathe.

Cold Water Temperatures

Cold waters are like a blanket that slows down a fish’s metabolism. As a result, they’ll have a hard time digesting their food and growing.

Moreover, low water temperatures make fish more susceptible to diseases such as ich and velvet making it even harder for them to grow in a healthy way.


Even though discus fish are social creatures, they still need their space. If you overcrowd your tank, it will cause stress and make it harder for them to get the food and oxygen they need. This will stunt their growth.

To avoid this, make sure to provide at least 10 gallons of water per fish. Also, don’t overstock your tank with any trivial decor items that your fish don’t need. Keep it clean and simple!

Low Oxygen Levels

Although discus fish prefer warm water conditions because it aids their metabolism and growth, too much heat can be detrimental. Warm temperatures lower the oxygen levels in the water, creating a stressful environment for your fish that prevents them from growing.

To make sure your fish have enough oxygen, use an air pump and airstone to aerate their tank. Also, make sure to do regular water changes to keep the water fresh.

Can Stunted Discus Grow?

A stunted discus can grow, but it will never reach its full potential size. That’s because the damage to their growth plates is permanent.

However, if you provide the ideal conditions and a high-quality diet, your fish will still be able to grow and live happy and healthy lives. Just don’t expect them to get as big as they would have if they aren’t stunted.

How to Identify Stunted Growth in Discus Fish?

To fix a problem, you need to first identify it. So, how can you tell if your discus fish are stunted?

There are a few key signs to look for:

  • Their body is similar to a football or bullet
  • Their eyes are large when compared to their whole body size
  • Their eyes are asymmetrical, where one eye is higher on the face than the other
  • Their eyes are different in size, where one eye is larger or smaller than the other

How to Solve Stunted Growth in Discus Fish?

Now that you know how to identify stunted growth in discus fish, it’s time to learn how to solve it.

Unfortunately, once a discus fish has been stunted, there’s no way to reverse the damage. That’s because their growth plates have been damaged and will never grow back. However, there are still things you can do to help your fish grow as much as possible.

To start, you need to provide the ideal conditions for growth. This includes a warm temperature, a high-quality diet, and plenty of space. Also, you should make sure there’s no ammonia or nitrites in the water and that the oxygen levels are high.

Finally, you need to be patient. It will take time for your fish to grow, so don’t expect them to reach their full potential size overnight. Just keep providing the ideal conditions and let nature take its course.

In case it is a genetic problem, there is no way to change it and the only thing you can do is accept it. But if the problem is due to environmental conditions, then you can definitely take steps to improve the situation.

Last Words

Discus fish are beautiful creatures that make a great addition to any aquarium fish. However, discus fry are also very sensitive and need the ideal conditions to thrive.

If you provide the ideal conditions and a high-quality diet, your fish will grow to their full potential size. Just remember to be patient as it will take time for them to reach their maximum size.

Do you have discus fish? How large are they? Let us know in the comments below!