A community tank is usually planned from the surface down — the centerpiece fish, the school, and then, almost as an afterthought, something for the bottom. That afterthought deserves better, because the floor of the tank is a neighborhood of its own with its own rules. The peaceful bottom-dwellers suit each other beautifully when their needs overlap, and quarrel or starve when a keeper stacks species that compete for the same square foot of sand.
Start with the schooling catfish: corydoras
If the bottom layer has a foundation species, it is the corydoras. A group of six or more of one kind — bronze, peppered, panda or any of the hardy species of similar size — will sift, rest and bustle together across the floor all day, peaceful with everything and each other. They set the terms for the whole layer: the substrate must be sand or smooth fine gravel to protect their barbels, and food must deliberately reach the bottom rather than being left to chance. Build around a cory group and most community tanks have their floor half solved on day one.
Add one character species, not three
The classic beginner error is buying one of everything — a pleco, two loaches, three otos — and ending with a crowded, competing floor of fish that each needed a group or a territory of their own. Choose one addition that fits the tank you actually have. Kuhli loaches, in a group of six or more, suit planted tanks with sand and cover. A single bristlenose pleco suits a larger tank that grows some algae and offers driftwood. Otocinclus, kept in a group, suit small, mature tanks where soft algae is genuinely present. One of those, chosen well, beats all three chosen hopefully.
The floor itself: substrate, space and shelter
Bottom-dwellers divide the floor between them only if there is floor to divide. A tall, narrow tank has the footprint of a much smaller aquarium, and its bottom layer should be stocked to the footprint, not the gallon count. Spread shelter — caves, wood, plant thickets — across the whole base rather than in one prized corner, so a pleco's chosen cave does not evict the corys from the only cover in the tank. Leave open sand between the shelters: the foraging runs across bare ground are where you will watch these fish earn their keep every evening.
Match the whole stack: temperature and feeding
Finally, check the overlaps. Corydoras species differ in temperature preference, kuhlis and bristlenoses sit in the middle tropical range, and otos dislike water that is either unstable or very warm; a community floor only works where all their ranges genuinely intersect with the fish above them. Feeding needs the same deliberate matching — sinking foods delivered after the main feed, algae present or wafers offered for the grazers, and enough floor-level portions that the slowest bottom-dweller eats every day, not just on the days the school above it is distracted.
Stocked this way, the bottom of a community tank becomes its most reliably entertaining layer, busy from lights-on to lights-out. Finding shops that keep these fish in proper groups and can tell one cory species from another is half the battle, and KinsLe's Pet Services Directory is there for exactly that: find trusted local pet businesses, connect with them, and stock the floor from people who keep it well themselves.