I have two discus as recent additions to my tank. They are 3 inches each and they are the only discus I currently have in my tank. I have been observing them for a week and one of them is constantly bullying the other especially during the feeding times.

The one which is getting bullied is hiding at the corner of my tank most of the times and it's getting stressed. It's even having less food.

How can I control or handle this kind of situation?

Also, I understand discus fish do better in groups. What is the minimum number of discus that should be kept together?

The tank is 40 Gallons and is well decorated.

  • can i ask what happened with these fish? We are in a similar situation. The only difference is our tank is slightly larger. Thanks Commented Jan 9, 2020 at 20:19

2 Answers 2


I have to strongly suggest taking these fish back to the store. I've kept discus for many years and bred discus in the past for roughly a decade. I can say with almost complete certainty that these fish are not going to survive and certainly are not going to achieve anything close to their potential in size and vibrancy.

Juvenile discus are handedly the most difficult freshwater fish to raise properly I've ever seen. If you cannot perform daily water changes upwards of 50% of the tank's total volume, and feed 4 - 5 times per day, you'll end up with unhealthy fish if they do survive to maturity and those that do will more than likely be permanently stunted. For any community tank, the only discus worth consideration are 5"+ full grown fish.

Secondly, even adults require substantially higher quality water than most fish keepers will ever come close to providing. I recommend no less than 50% water change per week. The water change volume is completely dependent on the stocking and observing the fish, I've seen heavily stocked community tanks requiring 50% every 2 days...

The crux with both juviniles and adults is the water needs to be seasoned, basically it needs to sit for 24 - 48 hours before being added to the tank so that the chemistry can stabilize and the keeper can ensure that Chlorine and Chloramines are properly removed, you must use a chlorine treatment for this or use reconstituted RO water. For juveniles this typically requires hours of work per day just in preparing water. Many professional breeders I've visited, change 100% - 200% of their tank water per day until their discus reach 5 - 6in.

Finally, discus are a community fish and should be kept in odd numbers with no less than 5 fish unless you have an established pair or a humongous tank, like 300 gallons or more. This is to minimize and distribute aggression between fish, they're cichlids so they're an inherently aggressive fish, and without enough fish to spread around aggression, you'll typically end up with a single fish without a large enough number to prevent the smallest from getting bullied.

So what you have right now is a situation where it's unlikely even an experienced keeper could get your fish to thrive. The tank is too small for a school of discus, bare minimum for an established pair, personally I would suggest 90 gallons is the absolute minimum I'd even consider for a small school of fish, and even with a 90 gallon tank, you're going to need to perform roughly 50 - 70% of the water per week for 5 discus and very few other tankmates.

Anyway, I hate to give advice like this, but I've just seen it too many times and seen too many fish stunted or outright not survive. Unless you're prepared to establish a fish only tank and feed and water change like you've never imagined or setup a large tank, both of these require a lot of work since you don't have a cycled tank ready to go, it's really unlikely you'll get good results with these fish. When they are stressed they are highly prone to diseases, stunting, and just not surviving.

  • Fantastic answer. By 'reconstituted RO water', do you mean RO water with the buffers (I think that's the right word) and trace minerals added back in?
    – Henders
    Commented Sep 16, 2017 at 20:42
  • 1
    Yes, either using something like Seachem Equilibrium if using strictly RO, or 50/50 RO and treated tap water, the latter is my preference. This is needed both for mineral content and that plain RO has no buffering capacity so can result in some whacky PH issues especially if a tank is also running CO2 for plants. For juveniles, plain treated and seasoned tap usually ends up with better growth, provided that the tap water PH isn't completely off the scale.
    – Jestep
    Commented Sep 18, 2017 at 14:58

I use tap water for my aquarium-bred discus. The 250 gallon tank which was my headboard has a dripper and an overflow. 24 gallons a day of untreated tap water is dripped through a carbon filter at about 45-50°. My PH is 7.2 and feed 2x a day morning and night. My fish are extremely healthy, both adult and juvenile. Aquarium is 5 years old and never lost a fish or had a sick fish(discus). I do add aquarium salt about once a month and treat with API general cure and EP ethro every 6 to 8 months to be safe. Not that anyone in this thread is wrong but definitely over board. My fish guy says discus people are crazy 90% of the time and make the hobby seem impossible.

While a lot of what is said holds validity, success with aquarium-bred discus isn't some impossible feat that only pros can enjoy. Water stability is more important than all of the above. Happy discussing.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.