I have a 75G fw tank that I would like to convert to sw. Current filtration is with 2 300 Aquaclear filters. Can these be used for marine? I was reading that the current light would be sufficient for some live rock and fish but not for corals etc. I would like to have a fairly large amount of rock say about 125lbs and a dsb of about 4 inches of fine live sand. I think this may be okay for the biological needs. I am not sure about the necessity of a protein skimmer as I will mostly have fish and very very few corals. Any help here would be appreciated. My other option is going to a 24G nanocube and starting from scratch?