What types of fish do you have? In my 75g fowlr I've currebtly got a melanarus wrasse, a coral beauty angelfish, a yasha goby (paired with a pistol shrimp), a black and white clownfish, and a copperband butterfly. With them I can put all sorts of stuff, and if you have fish like them you can as well. I've got conchs, cerith snails, trochus snails, nasasourus snails, astrea snails (breeding themselves in the tank right now), at least 6 different hermit crab species, 2 fire shrimp, 2 longspine urchins, 1 pencil urchin, 1 chocolate chip starfish, 1 African starfish, 1 arrow crab, a few emerald crabs, a horseshoe crab, and another crab I've blanked out on and can't remember the name, and more. For my reef tank a whole other set! You can get creative and don't be to shy, if you don't have corals there's not a lot to be worried about; they won't harm your fish, just make sure your fish don't harm them (fish like triggers and puffers will do some serious damage to a CC). Most fish are fine with them though. Take advantage of them, they really liven up your tank more than you could ever imagine!