Discus Minimum Tank Size
The minimum tank size for discus is 55 gallons. Here is why, plus group size and the best tankmates.
Quick answer
55 gallons
The minimum tank size for discus is 55 gallons. Keep a group of 5 or 6.
The recommended minimum tank size for discus is 55 gallons. Discus are large, social cichlids that grow to about 8 inches and need warm, pristine water in a group. A 55-gallon is the minimum for a small group, and bigger is better. Bigger is always better: a larger tank is more stable and more forgiving, so treat 55 gallons as a floor rather than a target.
Set up a 55-gallon discus tank
A 55-gallon (or larger) tank is the right starting size for discus.
Most of these species need a stable tropical temperature.
Cycle the tank and keep ammonia and nitrite at zero before adding livestock.
Why discus need at least 55 gallons
Discus are large, social cichlids that grow to about 8 inches and need warm, pristine water in a group. A 55-gallon is the minimum for a small group, and bigger is better. Tank size is not just about the fish fitting in the water; it is about swimming room, water stability, and bioload. A larger volume dilutes waste, holds temperature and chemistry steadier, and gives discus room to behave naturally. Cutting below 55 gallons tends to mean more stress, more aggression, and more frequent water problems.
| Detail | Discus |
|---|---|
| Minimum tank size | 55 gallons |
| Group / social needs | Keep a group of 5 or 6 |
| Recommended starting tank | 55-gallon or larger |
Group size and behavior
Keep a group of 5 or 6. This is a social species that feels secure only in a proper group, so plan the tank around the whole school rather than one or two individuals. A larger group also spreads out activity and reduces stress. For the full picture on diet, water parameters, and breeding, see the full discus care guide.
Good tankmates for discus
Discus generally do well with calm, similarly sized companions. A few reliable options:
- cardinal tetras
- sterbai corydoras
- german blue rams
Always confirm that any tankmate shares the same temperature and water-chemistry needs, and that your tank is large enough for everyone combined. Use the stocking calculator to check the full bioload before you add fish.
Plan the tank
Once you have settled on a tank, size the gear with the 55-gallon tank setup guide and confirm the volume with the minimum tank size calculator.
Frequently Asked Questions
What is the minimum tank size for discus?
The recommended minimum tank size for discus is 55 gallons. Discus are large, social cichlids that grow to about 8 inches and need warm, pristine water in a group. A 55-gallon is the minimum for a small group, and bigger is better. Treat that as a floor, since a larger tank is more stable and more forgiving.
Can you keep discus in a smaller tank?
Going below 55 gallons usually means more stress, more aggression, and faster swings in water quality. The extra volume of the recommended size dilutes waste and steadies temperature and chemistry, which keeps discus healthier. Bigger is better whenever you have the space.
How many discus should you keep together?
Keep a group of 5 or 6. This is a social species, so plan around the full group rather than one or two, and provide a tank large enough for the whole school.
What are good tankmates for discus?
Discus do well with calm, similarly sized companions such as cardinal tetras, sterbai corydoras, german blue rams. Always confirm shared temperature and water-chemistry needs, and run the full stock list through a stocking calculator so you do not overload the tank.
Planning or running a tank?
Use our free calculators and guides to get every number right.
Aquarium Planner: $39