it looks like you will need to do some research first. as for fresh water, you generally don't mix african cichlids with tropicals, you also shouldn't mix goldfish with tropicals( GF are very dirty). i'm thinking you probably want a "community" tank, with all peacefull fishes(cichlids are out!). this will give you a larger variety of fish to choose from. i wish i knew of a freshy site to refer you to, maybe someone else knows? but, a 75 would certainly have the potential to be a very nice community tank. if you get into live plants you will need some good lighting, expect to spend some money on that. as for filtration, on a fresh tank, i'd probably go with a canister filter. it would be a good idea to find a good reliable fish store were there are knowlegeable employees, who can answer your questions about stocking, and compatibility( appharently noone did this before, because anyone who works with fish could have told you that if you put that fish list in a 10G tank, that after several months, all you would most likely have left is one cichlid!) just research first, and remember, your better off spending your $ on quality equipment than getting too eager and stocking an inadequate tank with fish who are destined to die anyways. i guess what i'm saying is, do your research first, then buy your equipment, then be shure the tank is cycled, then start stocking it!