If you used all cured live rock this is probably the reason you only saw a small cycle in your tank. The bacteria that grows during the cycle actually lives on the surface of the rock,glass, and sand as opposed to in the water. So by using already cured LR
you got a good culture of bacteria already started. Your tank should be go and cycled by now and is probably ready for fish. Inverts like snails are actually just as sensitive to ammonia and nitrites as fish are so if they have been doing ok you should be good to go. Then again it can't hurt to try the algae wafer and check your levels just to be on the safe side.