If a breeding colony containing several fish is to be established, then it is recommended that at least one square foot of "floor space" should be allowed for each male and that at least one shell is available for each fish in the colony. While not always the case, many of the shell dwelling cichlids have adopted the practice of burying their shells until only the opening remains. This practice is more evident with wild imports and is often a key to spawning when all else fails. Ideally the tank floor should be covered with 2 to 3 inches (5 - 7.5 cm) of very fine gravel, preferably clean sand, such that each species may practice what comes naturally and bury their shell, the theory being this is to give added security from detection and prevent theft by such large cichlids as Lamprologus callipterus, an inhabitant of the same zone that has been observed carrying inhabited shells off in it's mouth back to it's own territory.
This gravel or sand substratum should be fine. Coral sand is adequate but silver sand is ideal. The water should be clean and well aerated using an appropriate air-operated sponge filter in the tank corner. Undergravel filters should be avoided since most shell dwellers spend tireless hours rearranging the gravel or sand in an aquarium only to result in exposing the filter and total disruption of the filter's effectiveness.
If a tank is to be established with no sand or fine gravel as substratum, then each shell should be placed on a shallow saucer full of sand to cater to the needs of these cichlids to excavate around the shell. Personally, I have witnessed an adult male push a shell as long as itself a distance of three inches across a sandy floor until the shell was positioned as the male required. Typically the fish will either excavate beneath the shell causing the shell to subside until all but the opening is apparent or cover the shell with sand, mouthful by mouthful or grain by grain, until the same result is achieved. A trick to removing these fish from their shell, without also taking the shell from the aquarium, is to place a nine-inch length of plastic pipe full of sand upright in the tank such that the shell can be placed on top of this pipe and yet still be fully submerged. Eventually the fish will leave the shell only to note its new position and to return to the floor of the aquarium where it feels more secure. The empty shell can now be removed from the top of the pipe and the fish caught, provided no other suitable refuges exist.