I have been reading the threads posted on octos and have been doing a little homework on them and i really want to give it a shot. I have heard mixed reviews(even my mother is trying to perswayed me in the other direction) about octos but want to do it. My 55g has been up for about 8-9 months now. I have a few questions: 1. Will my emporer 280, millineum 2000 and seaclone 150 protein skimmer be good enough filtration? 2. Is 190 watts too much lighting for him? 3. I have 4 corals; Brain, toadstool leather, frogspawn and a hammer head coral. Will they be alright with an Octo? 4. Since all my filtration means are hang-ons, will it be difficult to "seal" up the top on my tank? 5. I have heard some sites say that Ro/di water, what exactly is that? Those are a couple more than a few, sorry about that, just want to make sure everything is right. Thanks again for the help.