The short answer
Bottom-dwelling fish add life to the lower level of a tank and forage where other fish don’t reach. The best, most peaceful choices are:
- Corydoras (sociable catfish; keep six or more of one species)
- Kuhli loaches (shy, eel-like, best in groups)
- Bristlenose plecos (a manageable, algae-grazing pleco)
- Otocinclus and pygmy corydoras for nano tanks
Group fish need company
Most popular bottom dwellers are social shoalers. Corydoras and kuhli loaches feel safe and behave naturally only in a group of six-plus — kept alone they hide and fade. The main exception is the bristlenose pleco, which is fine on its own. Avoid the common pleco, a frequent mistake: it grows to 30 cm or more and produces huge amounts of waste, quickly outgrowing home aquariums. For a nano, scale down to pygmy corydoras or otocinclus.
Substrate and feeding matter
Corydoras and kuhli loaches root through the substrate with delicate barbels, so a soft sand or smooth, rounded gravel protects them from injury. Because they feed at the bottom, they can miss out when mid-water fish grab everything first — add sinking pellets and wafers so food actually reaches them. Provide caves and plants for cover, especially for shy loaches.
For the right group size, see how many corydoras to keep together and how many fish you can keep. Read the full corydoras care guide, browse the fish food hub for sinking foods, and see good tankmates for corydoras to build the community.