[BlueAbyss]

Should have waited for the cycle to be finished completely before adding any livestock, it's hard on them to live in an unstable (and slightly toxic) environment. Don't forget to feed your crabs and snails if there's nothing in the tank for them to eat... they will starve without algae and detritus for them to munch on. Feed lightly though, specially if your cycle isn't finished completely. And +1 on the weekly water change, I think regular water changes are overlooked a lot as a way to keep a tank healthy.

EDIT: Just noticed your test for ammonia at 0, awesome. Keep testing though, adding livestock will throw things off a bit again. Anything that eats produces ammonia, so we'll see if your cycle is indeed done.