pretty much all snails are fine, and freshwater clams need light i believe. If you're keeping fish in there too then i would stear clear of the crab, as they are opportunistic (think i spelled it right...) and will sometimes catch fish if they can. dont know about newts, but are they completly aquatic, or do they need land to be able to go on too? For shrimp, you could, i guess, get a bunch of ghost shrimp, but i dont really care for them...kinda ugly i think. Or you could get...aahh...i think its called a cherry shrimp? never had one, but i've heard they're really cool lookin, but they're like 2 or 3 bucks a pop. I cant say nothing about the frog either, but i've heard a lot of people say they dont recommend them.