Neolamprologus multifasciatus is the smallest known cichlid in the world and are affectionately called "multies." A colony of 6 multies live with us in a 29-gallon tank with sand for substrate, some rocks, some gravel pieces mixed in the sand, plastic plants, and 10 shells. If you’re considering what type of cichlid can go in a 10-gallon tank, multies may be the answer.
Males reach a maximum length of 1.5-2 inches, and females will grow to .75-1 inch. What they lack in size, they make up for in attitude. In the National Geographic video Lake Tanganyika - Jewel of the Rift, one is seen biting at the tail of a small crocodile who comes too close to its home. Multies live in the vacated shells of the snail Neothauma. A male will establish his territory around several shells and entice females to live in these shells, forming a small colony in his area. They literally live in the shells; they sleep in them, retreat to them when they're startled, spawn in them, and raise their fry in them.
Eggs are laid in the shell and protected until the fry develop. At first, the fry will stay in the shell. Then, as they venture out, they will stick close to the shell and gradually enlarge their "comfort" zone as they get larger. Since the females are so small, broods will contain only a few fry. And since the eggs are secretly deposited in the shell, the first sign of breeding activity may be when the fry leave the shell. As the fry develop, they will not eat or pick on their newer siblings. This allows several generations and sizes of fry to be observed in the colony.
The shells are not buried as other shell-dwellers do. They will dig a pit in and around the shell. In an aquarium, they will dig this pit down to the glass. The digging activity is amazing to watch. They will begin by scooping up sand in their mouth from one side of the shell. They swim some distance from the shell and drop the sand off (sometimes on a neighbor’s shell). Once they’ve made some headway with their mouth, they will force their way under the shell, swinging their entire body from side to side. A sand cloud forms as they bulldoze their way under the shell and out the other side.
They repeat these steps until the shell is to the bottom of the tank. It doesn’t matter how deep your sand is. When we started, I had 2 inches of sand in the bottom of the tank, because I thought that they would want to bury the shell. Amazingly, they dug down to the bottom of the tank, and covered up several shells in the process, and created a mountain of sand at the other side of the tank. We have also observed them lifting pebbles that looked heavier than the fish itself, and moving those around until they were satisfied with them. They certainly have specific preferences about their decorating.