well, i'm in the process of cycling my tank. it will be fish only w/ live rock. my mom who has 3 established tanks helps me out. we added the water, the rock, a hermit crab, and a brittle star (tho the guy at the lfs told me he may not survive the cycle). and you just let it go. yes top the tank off with some r/o water when it evaporates, but don't do a water change till you're all the way through your cycle. definitely do a search in the message boards for other similar threads, as everyone has advice. buy a test kit (i have a saltwater master liquid test kit). and check w/ your lfs to see if they offer any water testing, if they do they have probably been doing it for a long time and can tell you if your levels are off and what you can do to fix it. but definitely tell them that your tank is new, since you shouldn't play w/ any water levels during cycling...