Best Discus Tank Mates

What makes a good tank mate for discus?

A good discus tank mate thrives in very warm, soft water, eats calmly enough not to outcompete a shy fish, and is too large to be eaten. Discus (Symphysodon spp.) are disc-shaped cichlids from lowland Amazon floodplain lakes and flooded forests; Seriously Fish gives an adult length of 5.5 in (14 cm). Four criteria follow from the published sources.

1. Very warm water. Our discus range is 79–86 °F (26–30 °C), from Seriously Fish and FishBase. That lower limit sits above the upper limit of many community fish, so temperature decides most discus verdicts.
2. Soft water. Discus need pH 5.0–7.6 and 0–8 dGH. Livebearers and snails, which prefer hard, alkaline water, share little of that range.
3. Calm feeding. Aquarium Co-Op describes discus as slow, shy feeders that fast-feeding tankmates outcompete, and Seriously Fish and Co-Op both say the species is very skittish and needs cover and calm companions.
4. Not small enough to eat. Maidenhead Aquatics says tankmates must not be small enough for an adult discus to eat, and Shrimp and Snail Breeder says dwarf shrimp become discus food.

Discus are rated advanced in our data; Aquarium Co-Op calls them notorious for being extremely difficult to keep, so tank mates should add as little stress as possible. This page is one of our tank mates by species guides, which rank each species with the same method.

Which fish are the best discus tank mates?

The best discus tank mates are the few warm-water species that are also too large to eat, and only a handful of species in our data clear both bars. Each is described below with the evidence behind its score.

Angelfish

Angelfish score 8/10 with discus. Both are Amazon cichlids, they share 79–86 °F (26–30 °C) and pH 6.0–7.6, and the angelfish, at 6 in (15.2 cm), is close to the discus in size. The pairing needs 125 US gal (473 L) because the angelfish is semi-aggressive, and Seriously Fish notes that angelfish squabble with their own kind and chase fish from spawning sites. The angelfish tank mates guide covers the pairing from the angelfish side.

Betta

Bettas also score 7/10, because their range of 72–86 °F (22–30 °C) reaches as high as the discus range and their pH ranges overlap widely, at pH 6.0–7.6. Treat that result with care. Seriously Fish advises keeping bettas alone and calls them unsuitable for a standard community, and the pair needs 125 US gal (473 L). The ranked list of betta fish tank mates shows which companions suit a betta better.

Cardinal tetra

Cardinal tetras score 7/10, with a caution verdict. They share 79–84 °F (26–29 °C) and a wide pH band, and Aquarium Co-Op lists cardinals as suitable discus tankmates. The caution comes from size: a cardinal grows to only 1.4 in (3.6 cm), and Maidenhead Aquatics says tankmates must not be small enough for adult discus to eat. Practical Fishkeeping suggests 77–82 °F for a Rio Negro cardinal biotope, which overlaps the cool end of the discus range.

Guppy and molly

Guppies score 7/10 and mollies 6/10. Both share 79–82 °F (26–28 °C), but both prefer harder water than discus. Guppies share pH 7.0–7.6, and mollies only pH 7.5–7.6; Seriously Fish and Aquarium Co-Op say mollies become disease-prone in soft or acidic water, which is exactly what discus are kept in.

How do wild and captive-bred discus change the tank mate list?

Farm-raised discus are often kept warmer than the wild range, and that warmer figure removes most remaining tank mates. Our displayed range of 79–86 °F (26–30 °C) comes from Seriously Fish and FishBase, but the sources disagree at both ends.

Temperature

Maidenhead Aquatics gives 81–86 °F, and Aquarium Co-Op recommends 85–86 °F because farm-raised discus are kept warm. At that higher figure, cardinal tetras (73–84 °F (23–29 °C)) and guppies (68–82 °F (20–28 °C)) are above their upper limits, which leaves angelfish (75–86 °F (24–30 °C)) and bettas as the only fish in our data whose ranges still reach it. Read the temperature guide for tropical species before choosing a heater setting for a mixed tank.

pH and hardness

The pH and hardness sources disagree widely. Seriously Fish gives pH 5.0–7.0 and Maidenhead Aquatics pH 6.0–6.5, while Aquarium Co-Op says both wild and captive-bred discus do well at pH 6.8–7.6. Aqualog records wild discus water at pH 4–5 with no measurable hardness, and Seriously Fish gives 0–5 dGH, against Maidenhead’s upper limit of 8 dH and Co-Op’s soft to medium. The practical effect for tank mates is that Co-Op’s more neutral water suits livebearers such as guppies better, while the soft, acidic water recorded for wild habitats favours soft-water fish only. The aquarium pH guide explains how to measure and hold a target.

Our data does not separate wild-caught from captive-bred discus as different entries, so the scores on this page use the consensus range. If you keep farm-raised discus at Co-Op’s temperature, re-check each tank mate against that figure rather than against the table.

Which fish should never live with discus?

Fish that cannot live in very warm water should never live with discus, and neither should predators or fish small enough to eat. Most species in our data fail on temperature alone.

No shared temperature

Neon tetras, platies, zebra danios, goldfish and mystery snails share no temperature range with discus. Neon tetras, for example, need 70–77 °F (21–25 °C), and goldfish 59–70 °F (15–21 °C). Discus score 3/10 with neons, and Maidenhead Aquatics’ warning about fish small enough to eat applies as well.

Ranges that barely meet

Corydoras, kuhli loaches, bristlenose plecos, harlequin rasboras, GloFish tetras, dwarf gouramis and Endler’s livebearers all have upper limits that reach the discus range by only a degree or two. Corydoras, at 70–81 °F (21–27 °C), share just 79–81 °F (26–27 °C), and bristlenose plecos 79–79 °F (26–26 °C). A shared range that narrow leaves no margin for heater drift, and at Aquarium Co-Op’s farm-raised temperature it disappears. These fish are better placed in the tanks described in the guides to bristlenose pleco tank mates and kuhli loach tank mates.

Oscars

Oscars score 3/10. They share only 79–80 °F (26–27 °C), grow to 14 in (35.6 cm), and Seriously Fish and Aquarium Co-Op describe them as predators of any fish small enough to swallow, which includes a discus. The guide to compatible tank mates for oscars covers the large, robust fish that suit them.

Are discus aggressive toward tank mates?

No, not toward other species. Discus are cichlids, and cichlids have a reputation for aggression, but Seriously Fish calls the discus peaceful and shy, and Maidenhead Aquatics reports minimal aggression toward suitable companions. Our discus data records its temperament as peaceful.

The aggression that does occur is aimed at other discus. FishBase notes territorial behaviour when breeding, and Aquarium Co-Op says bullying appears in small groups, which is why it starts with 10–12 juveniles rather than a pair. The real risk with tank mates runs the other way: Aquarium Co-Op says fast-feeding tankmates outcompete discus for food, and Seriously Fish and Co-Op say this skittish fish needs calm companions and cover.

How many discus should you keep together?

Keep at least 6 discus. Seriously Fish says the species needs a group, and Aquarium Co-Op starts with 10–12 juveniles in a 75-gallon tank and thins the group to about six adults as they grow. Crampton (2008), in a field study published in Neotropical Ichthyology, records wild discus gathering in dry-season colonies of hundreds among sunken branches.

The group itself takes most of the space in a discus tank, so tank mates come second. Discus breeding is rated hard in our data: Crampton describes eggs laid on submerged roots with care of eggs and larvae, and Aquarium Co-Op says raising fry is very time- and labour-intensive. Captive discus typically live 3–5 years according to Crampton, though Aqualog reports one reaching 17 years.

What tank size do discus and their tank mates need?

Discus pairings with peaceful fish need 75 US gal (284 L) in our data, and pairings with angelfish or bettas need 125 US gal (473 L). The shared figure takes the larger of the two species’ minimum tanks, adds a margin of one half when one species is semi-aggressive, and rounds up to the next common tank size.

Under 55 gallons

No discus tank mate fits a 10, 20 or 29-gallon tank in our data, because the discus minimum alone is 67 US gal (254 L). If you have a small tank, the guide to the best fish for a 10-gallon community tank is a better starting point than discus.

55 to 75 gallons

Our minimum of 67 US gal (254 L) comes from Seriously Fish’s 255-litre tank for a few juveniles or a breeding pair. Aquarium Co-Op recommends 75 gallons for a group, with 55 possible only with frequent water changes, and Aqualog gives 216 litres, about 57 US gallons, as the minimum for a pair. A group of discus with cardinal tetras or guppies calculates at 75 US gal (284 L).

125 gallons

Angelfish or a betta with discus need 125 US gal (473 L) under our method. The stocking calculator checks a full discus community against a given tank.

Can discus live with shrimp and snails?

Discus are a poor match for both, for different reasons. Shrimp are eaten, and snails need cooler, harder water.

Shrimp

Shrimp and Snail Breeder says dwarf shrimp become discus food. Cherry shrimp score 3/10 and amano shrimp 3/10; the cherry shrimp’s range of 70–79 °F (21–26 °C) also meets the discus range only at its upper limit. The guide to cherry shrimp tank mates lists fish that leave shrimp alone.

Snails

Nerite snails score 3/10 and mystery snails 3/10. No source in our discus data says discus eat snails; the problem is water. Mystery snails need 70–78 °F (21–26 °C), below the discus range, and nerites need pH 7.2–8.0, harder and more alkaline than most discus water. Our snail compatibility guide lists better companions.

To score any species not on this page against discus, use the species compatibility checker, which draws on the same data.