Best discus tank mates: top 7 compatible species at 29°C (84°F)
The best tank mates for discus — a pillar guide with 7 species that thrive at 28–30°C (82–86°F): cardinal tetra, rummynose, Corydoras sterbai, Ancistrus, ember tetra, lemon tetra, hatchetfish.
Quick summary
- Only 7 species are compatible long-term at 29°C (84°F).
- Top 3: cardinal tetra, rummynose tetra, Corydoras sterbai.
- Don't use common neon (Paracheirodon innesi) — it prefers 24°C (75°F).
- The only Corydoras for discus: sterbai (tolerates 30°C / 86°F).
- Bottom: Ancistrus (bristlenose), NOT a common pleco.
- At least 10 fish per school (cardinals, rummynose, ember).
In short
- Only 7 species are compatible with discus long-term at 29°C (84°F).
- Top 3: cardinal tetra (Paracheirodon axelrodi), rummynose tetra (Hemigrammus bleheri), Corydoras sterbai.
- NOT the common neon tetra (P. innesi) — it prefers 24°C (75°F) and dies at 29°C (84°F).
- The only Corydoras for discus: sterbai. Aeneus, paleatus and julii suffer at 29°C (84°F).
- Bottom: Ancistrus (bristlenose). NEVER a common pleco (40–50 cm / 16–20 in, attacks the slime coat).
- Schools of at least 10 for cardinals / rummynose / ember.
What you'll learn
Tank mates for discus (Symphysodon) must be picked against 3 strict criteria: tolerance of 28–30°C (82–86°F), pH 6.0–7.2 and a peaceful temperament (zero fin-nipping). This pillar guide shows you the 7 species that meet every condition, the recommended school size and what to avoid even when the shop tells you they "go together."
💱 The "EU price 2026" figures below are rough European retail references only — not verified global prices. Costs vary a lot by country, species quality and supplier, so always check your local market.
What makes an ideal discus tank mate
✅ Tolerates 28–30°C (82–86°F) long-term (not just "survives") ✅ Lives at pH 6.0–7.2 and moderate TDS (100–300 ppm) ✅ Peaceful — doesn't nip long fins (the fin-nipper test) ✅ Doesn't compete aggressively for food ✅ At most 8–10 cm (3–4 in) as an adult (in proportion with the discus) ✅ A schooling species (10+) or a solitary, peaceful pleco ✅ Compatible with the discus slime coat (doesn't eat it)
Top 7 verified tank mates
1. Cardinal tetra (Paracheirodon axelrodi) ⭐ #1
Native to the Rio Negro — the same biotope as wild discus. An electric-blue + bright-red stripe along the whole body.
| Parameter | Value |
|---|---|
| Temperature | 24–30°C (75–86°F) ✅ |
| pH | 4.5–7.0 |
| Adult size | 4–5 cm (1.6–2 in) |
| Minimum school | 10–15 fish |
| EU price 2026 | €2–4 each |
⚠️ Common confusion: the common neon tetra (P. innesi) is NOT a cardinal. Innesi prefers 22–26°C (72–79°F) and slowly dies at 29°C (84°F).
2. Rummynose tetra (Hemigrammus bleheri) ⭐
Silvery fish with an intense red nose. They move in tight schools — a spectacular visual effect.
| Parameter | Value |
|---|---|
| Temperature | 26–30°C (79–86°F) ✅ |
| pH | 5.5–7.0 |
| Adult size | 4–5 cm (1.6–2 in) |
| Minimum school | 10 fish |
| EU price 2026 | €3–5 each |
Bonus: the red nose becomes more intense when the water is good — a natural quality indicator.
3. Corydoras sterbai (Corydoras sterbai) ⭐
The only Corydoras species that thrives at 29–30°C (84–86°F) long-term. Golden-brown with white spots on the head.
| Parameter | Value |
|---|---|
| Temperature | 26–30°C (79–86°F) ✅ |
| pH | 6.0–7.6 |
| Adult size | 6–7 cm (2.4–2.8 in) |
| Minimum school | 6 fish (MANDATORY) |
| EU price 2026 | €8–15 each |
⚠️ NOT Cory aeneus, paleatus, julii or panda — all prefer 22–26°C (72–79°F) and get sick quickly at 29°C (84°F).
4. Ancistrus (Ancistrus sp.) — bristlenose pleco ⭐
The best pleco for discus: small, peaceful, eats algae without attacking the fish's slime coat.
| Parameter | Value |
|---|---|
| Temperature | 23–29°C (73–84°F) ✅ |
| pH | 6.0–7.5 |
| Adult size | 10–15 cm (4–6 in) |
| Number | 1–2 fish (males are territorial) |
| EU price 2026 | €10–25 each |
❌ NOT a common pleco (Pterygoplichthys) — it reaches 40–50 cm (16–20 in) and eats the discus slime coat at night → lesions + secondary infections.
5. Ember tetra (Hyphessobrycon amandae)
Tiny bright-orange fish. Very peaceful, perfect for planted tanks.
| Parameter | Value |
|---|---|
| Temperature | 24–29°C (75–84°F) ✅ |
| pH | 5.5–7.0 |
| Adult size | 2–2.5 cm (0.8–1 in) |
| Minimum school | 15–20 (for effect) |
| EU price 2026 | €2–3 each |
6. Lemon tetra (Hyphessobrycon pulchripinnis)
Golden-yellow, robust fish, ideal for beginners.
| Parameter | Value |
|---|---|
| Temperature | 23–28°C (73–82°F) ⚠️ (upper limit) |
| pH | 5.5–7.5 |
| Size | 4–5 cm (1.6–2 in) |
| Minimum school | 8–10 |
| EU price 2026 | €2–4 each |
⚠️ At a constant 29–30°C (84–86°F) they can be stressed long-term. Better suited to discus tanks kept at 28°C (82°F).
7. Marbled hatchetfish (Carnegiella strigata)
Surface fish — the one zone of the tank that discus don't occupy.
| Parameter | Value |
|---|---|
| Temperature | 24–30°C (75–86°F) ✅ |
| pH | 5.0–7.0 |
| Size | 3–4 cm (1.2–1.6 in) |
| Minimum school | 8–10 |
| EU price 2026 | €4–7 each |
⚠️ A tight-fitting lid is mandatory — they jump out of the tank instantly.
Comparison table — compatibility at 29°C (84°F)
| Species | Max temp | Zone | School | Recommendation |
|---|---|---|---|---|
| Cardinal tetra | 30°C (86°F) | Mid-top | 10–15 | ⭐⭐⭐⭐⭐ |
| Rummynose | 30°C (86°F) | Mid | 10+ | ⭐⭐⭐⭐⭐ |
| Cory sterbai | 30°C (86°F) | Bottom | 6+ | ⭐⭐⭐⭐⭐ |
| Ancistrus | 29°C (84°F) | Bottom/decor | 1–2 | ⭐⭐⭐⭐⭐ |
| Ember tetra | 29°C (84°F) | Mid-top | 15–20 | ⭐⭐⭐⭐ |
| Hatchetfish | 30°C (86°F) | Surface | 8+ | ⭐⭐⭐⭐ |
| Lemon tetra | 28°C (82°F) | Mid | 8+ | ⭐⭐⭐ |
| ❌ Common neon | 26°C (79°F) | — | — | NO |
| ❌ Cory paleatus | 26°C (79°F) | — | — | NO |
| ❌ Common pleco | 30°C (86°F) | — | — | NO (attacks slime coat) |
Golden rules for a community tank
- The discus comes first. Don't lower the temperature to keep fragile species — choose species that thrive at 29°C (84°F).
- Schools of at least 10 for cardinals / rummynose / ember — below 10 they're stressed and nip.
- Gradual introduction: cory + pleco weeks 1–2, tetra weeks 3–4, discus week 5+.
- 4-week quarantine for any new species (Hexamita, Camallanus from guppies/angelfish).
- Test nitrates weekly — keep below 20 ppm. Above = overstocked.
Example 300L (79 US gal) setup (recommended)
| Species | Number | Zone |
|---|---|---|
| Adult discus | 6 | Mid |
| Cardinal tetra | 15 | Mid-top |
| Rummynose tetra | 10 | Mid |
| Cory sterbai | 6 | Bottom |
| Ancistrus bristlenose | 1 | Bottom/decor |
Total: 38 fish — nitrates <10 ppm, zero aggression, spectacular visibility.
Common mistakes to avoid
❌ "The shop kept them together, so they're fine" — the shop keeps them at 24–25°C (75–77°F) temporarily. At home at 29°C (84°F), tiger barbs and common plecos show their true colors. ❌ "I'll get 3 cardinals and see how they do" — below 10 they're stressed and don't school. You pay more in losses than on the right group. ❌ "Cory paleatus is cheaper than sterbai" — at 29°C (84°F), paleatus dies in 3–6 months. Sterbai lives 5+ years. ❌ Adding angelfish — see discus + angelfish — Hexamita risk.
Checklist before buying tank mates
- ☐ The species' optimal temperature includes 29°C (84°F)
- ☐ Preferred pH 6.0–7.2
- ☐ Adult size under 10 cm (4 in)
- ☐ NOT a fin-nipper (check "does X nip fins")
- ☐ Tank large enough for the minimum school (10 cardinals = extra bioload)
- ☐ A 4-week quarantine available
- ☐ The discus are already settled (at least 4 weeks in the tank)
- ☐ Filtration handles the extra load (flow 4–6× volume/h)
What to do next
📚 Learn more:
- How many discus in an aquarium — table by volume
- Discus-only vs community aquarium
- Fish to avoid with discus — the blacklist
- Bottom feeders for discus — Cory + Ancistrus + L-numbers
- Discus + angelfish — why not
🧮 Calculate:
- Stocking calculator — how many fish fit in your volume
- Aquarium volume calculator — check the real capacity
🛒 Buy:
- Verified discus breeders — discus as the priority
- Food for tetra and cory
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