Feeding an ancistrus (pleco): vegetables, driftwood and the 'cleaner fish' myth
Ancistrus and other plecos are often sold as "cleaner fish" supposed to live off tank algae. That is a stubborn and dangerous myth: an underfed ancistrus wastes away. A reference study on wood-eating catfishes of the genus Panaque even showed that species which rasp wood barely digest any of it and draw most of their energy from the biofilm and micro-organisms coating it (research on Google Scholar). Find our other pointers in the food section.
A mostly plant-based, fibrous diet
The ancistrus (Ancistrus sp.) is largely herbivorous and detritivorous. Its base: special pleco sinking wafers, rich in spirulina and plant matter, supplemented with fresh vegetables. Tank algae are only a side dish, never a sufficient ration, especially in a well-kept aquarium where they are scarce.
Which vegetables to offer
Courgette, cucumber, spinach, shelled peas or a piece of sweet potato, blanched briefly and weighed down at the bottom, are much appreciated. Remove leftovers after 24 hours to keep them from fouling the water. Given in the evening, when the ancistrus is active, these vegetables cover a good share of its fibre and plant needs.
The role of a piece of driftwood
Submerged driftwood is not just decor: the ancistrus rasps it and grazes the biofilm, a natural behaviour important for its digestion and for wearing down its sucker mouth. Choosing safe wood is essential, as explained in our guide to algae-eating fish and snails. Without wood, the animal is deprived of a key part of its environment.
Not a cleaning crew
An ancistrus eats some algae and leftovers, but it replaces neither water changes nor maintenance: it produces plenty of waste itself. The idea of a fish that "cleans the tank" breeds bad habits. For a real algae-control plan, see our guide to algae eaters, and remember a dedicated diet stays essential, just as for feeding an angelfish.
Frequently asked questions
Can an ancistrus live on tank algae alone?
No: algae are never enough, especially in a clean tank. It needs plant wafers and fresh vegetables to meet its needs.
Does it really need wood in the tank?
Yes, safe driftwood lets it graze biofilm and wear down its mouth: it is an important part of its wellbeing, not a mere decorative touch.
When should I give vegetables?
In the evening, as lights-out approaches, since the ancistrus is rather nocturnal. Remove leftovers the next day to protect water quality.
This guide is part of Planète Pets’s Fishkeeping universe. Our advice is general in nature: for any health concern, your veterinarian remains the only reference.