Discus Stocking
Minimum 55 gal · 6" adult · medium bioload · peaceful.
Estimated bioload
65%
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Bioload-based: it weighs adult size and waste output, not the oversimplified "1 inch per gallon" rule.
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Keeping Discus
The Discus grows to about 6 inches and needs a minimum of 55 gallons. Its bioload is medium, meaning it produces a moderate amount of waste for its size, a key factor the "one inch per gallon" rule ignores. It's a schooling species, so keep at least 6 together or they'll be stressed. Temperament is peaceful, making it a good community fish. Use the calculator above to see how a group fits your tank's real volume before you buy.
Before you add this species
- What bioload actually isWhy a medium-waste fish counts ×1.7 per inch
- Cycle the tank firstFishless cycling, step by step
Tanks that clear the 55-gallon minimum
Real inside dimensions and filled weight for the standard sizes that can house a Discus.
- 55 gallon tank48" × 13" × 21"
- 75 gallon tank48" × 18" × 21"
- 90 gallon tank48" × 18" × 24"
Species to plan alongside the Discus
Closest on temperament and tank-size requirement. Run the whole list through the calculator before you buy: bioload adds up across species, not per species.
- Common / Comet Goldfish55 gal min · 12" adult · high bioload · peaceful
- Fancy Goldfish30 gal min · 8" adult · high bioload · peaceful
- Molly20 gal min · 4" adult · medium bioload · peaceful
- Corydoras Catfish20 gal min · 2.5" adult · low bioload · peaceful
- Swordtail20 gal min · 4" adult · low bioload · peaceful
- Cherry Barb15 gal min · 2" adult · low bioload · peaceful
Frequently asked questions
What size tank does a Discus need?
At least 55 gallons. They're a schooling fish, so keep a group of 6 or more.
Is the Discus peaceful?
Temperament is peaceful. Reaching about 6" as an adult with a medium bioload, plan tankmates and filtration accordingly.
Keep going with the same pet
Not sure of your tank's exact gallons? Measure it with the aquarium volume calculator first.
Your dog's age in human years, breed-size adjusted, not the ×7 myth.
Your cat's age in human years using the real feline curve, not the ×7 myth.
How much to feed: daily calories and cups by weight, activity and life stage.
Tank gallons and liters from your dimensions: rectangle, cylinder, hex and more.