I have no idea what "shellies" or "multies" are either.
Shellies or Shell Dwellers are a group of species from Lake Tanganyika. They tend to be small (less than 3inches) and live in and around empty snail shells on the lake floor. They can be very interesting behavior wise.
Multies is the shorthand for 'Lamprologus' multifasciatus. They area lovely little shell dweller. one of their most endearing attributes is that they are truely a colonial fish. Meaning they really live in a colony. A small group of adults will set up small territories on the tank floor. When they have fry, everybody helps protect them. As these fry grow and new fry are born, the older fry help out with the smaller ones.
There are many species of Shell Dweeler that would work in a tank of your size. Some work best in pairs, some as trios or small groups and a few, like the multies, will blossom into whole colonies.