Discus are the “king of the aquarium” — large, disc-shaped cichlids in dazzling colours that many keepers aspire to. They are also demanding: they need warm, spotlessly clean, soft water and are best left until you have a season or two of experience behind you. Get the conditions right, though, and nothing else in freshwater looks like them.
Here is what discus actually need.
- Discus are advanced-level cichlids needing warm (28–30 °C), soft, pristine water.
- Keep a group of five or more in a 250-litre-plus tank with large weekly water changes.
- Hard-water UK areas may need RO water to hit the soft, acidic conditions discus require.
- Choose only heat-tolerant, peaceful tank mates like cardinal tetras and sterbai corydoras.
Quick facts
- Adult size: 15–20 cm
- Tank size: 250 litres minimum for a group
- Water: pH 6.0–7.0, soft, 28–30 °C (warmer than most fish)
- Lifespan: 10+ years
- Difficulty: advanced
Why discus are demanding
Discus need three things most fish tolerate the absence of: high heat (28–30 °C, which excludes many tank mates), pristine water (near-zero nitrate, meaning large frequent water changes), and soft, acidic water. In hard-water UK areas you may need RO water — see how to lower pH. They are also shy shoaling fish that must be kept in groups of five or more.
Tank setup and feeding
Use a 250-litre-plus tank with an oversized filter and a strong 300W heater. Do 30–50% water changes weekly (breeders do it daily). Test rigorously with a good test kit.
Feed a varied diet of discus granules, frozen bloodworm and beefheart mixes several times a day for young fish.
Tank mates
Choose heat-tolerant, peaceful fish: cardinal tetras, rummynose tetras, sterbai corydoras and bristlenose plecos. Avoid aggressive cichlids, fin-nippers and any fish that can’t handle 29 °C.
Frequently asked questions
Are discus fish hard to keep?
Yes — they are considered an advanced fish. They need high heat, soft acidic water and pristine conditions with large frequent water changes, so they are best kept after a season or two of experience.
What temperature do discus need?
28–30 °C, warmer than most tropical fish. This high requirement limits which tank mates can live with them.
How many discus should be kept together?
At least five. Discus are shy shoaling fish that become stressed and bully each other in smaller groups.
— Jaqline Smalling, FishForever
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