There's all kinds. First theres a bunch of different types of snails to use each do a little different things. Some for the rocks and wall and some for the sand. Peppermint shrimp are good and some blue and red leg hermit crabs. Maybe even a sand sifting fish like a watchman goby. There's a few different kinds. Remember to get some small snails to for the hard to reach areas. Dont worry they will grow.