Bottom feeders for discus: Cory sterbai, Ancistrus, L-numbers

In short

• Bottom feeders ≠ cleaners. They need dedicated feeding (sinking tablets, wafers).
• The only Corydoras for discus: sterbai (confirmed tolerance of 29–30°C / 84–86°F).
• Top pleco for discus: Ancistrus bristlenose (max 15 cm / 6 in, peaceful, eats algae).
• Premium L-numbers: L134, L200, L201 — tolerate 29°C (84°F).
• ❌ FORBIDDEN: common pleco (40–50 cm / 16–20 in, attacks the slime coat), Gyrinocheilus (aggressive), Cory paleatus/aeneus/julii.
• Feed in the evening after lights-out — bottom feeders are nocturnal.

What you'll learn

Bottom feeders are an optional but very useful component of a discus aquarium — they help consume food leftovers and algae, rounding out the lower zone of the tank. The catch: most bottom feeders prefer 22–26°C (72–79°F), and at 29°C (84°F) (the required temperature for discus) they suffer long-term. This guide shows you exactly which species cope, what to avoid and how to feed them correctly.

💱 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 a bottom feeder suitable for discus

✅ Tolerates 28–30°C (82–86°F) long-term (not just "survives") ✅ Peaceful — doesn't attack the discus ✅ Doesn't eat the discus slime coat (disqualifier: the common pleco) ✅ Doesn't dig excessively (substrate mess) ✅ Reasonable size: max 15 cm (6 in) for a pleco, max 7 cm (2.8 in) for a Cory ✅ A schooling species (Cory) or a peaceful solitary one (Ancistrus, L-numbers)

Top choices for discus

1. Corydoras sterbai (Corydoras sterbai) ⭐ #1 RECOMMENDED

The only Corydoras species that thrives at 29–30°C (84–86°F) long-term. All other Cory prefer 22–26°C (72–79°F).

Why ONLY sterbai?

Role: consumes leftovers on the bottom + eats fallen dry food. They're NOT "cleaners" — they need dedicated sinking tablets.

2. Ancistrus (Ancistrus sp.) — "bristlenose pleco" ⭐

The most popular pleco for a discus aquarium. Small, peaceful, effective on algae.

Eats algae off the glass, decor and plants (Anubias). Does NOT attack the fish's slime coat.

⚠️ Important: 2 male Ancistrus in a tank under 300L (79 US gal) = territorial conflict. 1 male + 1 female or 2 females works better.

3. L-numbers (special Amazonian plecos)

Plecos collected from the Amazon — many tolerate 29°C (84°F) perfectly and are premium-looking.

L134 Leopard Frog pleco (Peckoltia compta) ⭐

Yellow patterns with black spots — visually spectacular.

L200 Green Phantom pleco (Hemiancistrus subviridis)

L201 Inspector pleco (Hypancistrus inspector)

⚠️ Avoid: L046 Zebra pleco (Hypancistrus zebra) — although it tolerates the temperature, it's extremely shy, doesn't adapt well to a community tank and is very expensive (€200–400).

4. Otocinclus (Otocinclus affinis / vittatus) ⚠️ — with reservations

Small fish (3–4 cm / 1.2–1.6 in) that eat fine algae.

The problem: they prefer 24–26°C (75–79°F). At 29°C (84°F) they can survive, but they're stressed long-term — a suboptimal choice for discus.

FORBIDDEN bottom feeders

❌ Common pleco (Pterygoplichthys pardalis / gibbiceps) — reaches 40–50 cm (16–20 in), attacks the discus slime coat at night → lesions + secondary Columnaris.

❌ Chinese algae eater (Gyrinocheilus aymonieri) — aggressive, attacks the flanks of large fish for their slime coat.

❌ Corydoras paleatus / aeneus / julii / panda — don't tolerate 29°C (84°F) long-term.

❌ Kuhli loach (Pangio kuhlii) — hides permanently (you can't tell if it's eating), prefers a strict pH 6.0–6.5, hard to monitor.

❌ Yoyo loach / Clown loach — too aggressive at feeding, sometimes bite, reach 30 cm / 12 in (clown).

❌ Synodontis — aggressively nocturnal, disturbs discus resting on the bottom.

Feeding bottom feeders correctly

Bottom feeders do NOT feed only on the discus's leftovers. They need dedicated food:

For Corydoras

• Sinking carnivore tablets (Sera Catfish Chips, Tetra Wafer Mix Original, JBL NovoFect)
• Frozen bloodworms (1–2× / week)
• Frozen Daphnia
• Feed 2–3 times/week in the evening, after lights-out

For plecos (Ancistrus, L-numbers)

• Sinking pleco tablets (Sera Spirulina Tabs, Hikari Algae Wafers, JBL NovoPleco)
• Blanched vegetables (30 sec, then cooled): zucchini, cucumber, spinach, shelled peas
• Softwood (driftwood) — Ancistrus and L-numbers rasp cellulose for digestion
• Feed in the evening after lights-out
• Replace vegetables after 24h (don't let them rot)

Ideal setup for 300L (79 US gal)

Total bottom: 7–8 fish. A balanced tank, never overstocked in the lower zone.

Common mistakes

❌ "I'll buy 2 Cory to start and see how they do" — Cory below 6 are stressed, don't school and die in 3–6 months. At least 6 from day one. ❌ "I'll keep 2 male Ancistrus" — Territoriality, fights. 1 male + 1 female or 2 females. ❌ "A common pleco is cheaper" — It will destroy the discus in 3–6 months. A false economy. ❌ "Bottom feeders eat leftovers, they don't need feeding" — They starve within months. Dedicated evening feeding. ❌ Cory paleatus at 29°C (84°F) — They die in 6–12 months from disease (Ich, gill problems) due to the incompatible temperature.

Checklist before buying bottom feeders

• ☐ The species tolerates 28–30°C (82–86°F) long-term
• ☐ Cory: at least 6 fish from day one
• ☐ Ancistrus: NOT 2 males in the same tank under 300L (79 US gal)
• ☐ Common pleco FORBIDDEN (check for Pterygoplichthys species)
• ☐ A tank with softwood (for Ancistrus + L-numbers)
• ☐ Sinking tablets + vegetables available for feeding
• ☐ A 4-week quarantine for any newcomer
• ☐ Compatible substrate (fine sand for Cory — not sharp gravel)

What to do next

📚 Learn more:

• Best discus tank mates — rounds out the middle zone
• Tetra for discus
• How many discus in an aquarium
• Fish to avoid with discus — the blacklist
• Discus aquarium substrate — fine sand for Cory

🧮 Calculate:

• Stocking calculator — check the total load

🛒 Buy:

• Sinking food for bottom feeders — Sera, Tetra, JBL
• Fine sand substrate