There are some cool bottom dwelling fish like cories and loaches, but if you don't want those you could always go with larger snails, dwarf shrimp, dwarf crayfish. Not sure what you have in mind as far as stocking the tank i.e. the types of fish. Some of them may not be suitable with what I recommended. Angels would most likely go after dwarf shrimp unless you get something like Amanos, ghost shrimp, or some other type of shrimp that they can't really see well. Providing lots of hiding places for them in the form of vegetation like mosses is key in keeping an established colony going in the tank.