I just bought my first tank It is a used 75 gallon tank. Going to pick it up tomorrow. According to the guy it has 65 pounds of live rock, a crushed coral bed, and an aqua clear filter(all for $250). I already know that I am planning on replacing the coral bed with mostly sand and possibly a small bag of live sand to seed it. I also want more live rock. What I am wondering is if I should switch to a sump and protein skimmer system, or if it would be adequate to just run this filter with the live rock and get a backpack skimmer? Any thoughts on this or other suggestions?