Actually, a 75 gallon isnt really the best aggressive tank, especially not for triggers. Although they can LIVE in a 75 gallon, they will not "thrive", as in live "happily". They need a lot of swimming room, even at a young age, and can become quite temporamental in spaces like that. Good choices for that tank can be eels, maybe a russels or dwarf lion and MAYBE some wrasses, although wrasses like to have their swimming room as well. I would advise against groupers cuz they get very large and yield high bioloads. Yes, get as much equipment as you can, a high water flow, a good skimmer, plenty of live rock. My best advice, like always, is to get the largest tank u can affrod to have. Cuz in this hobby, yer always hungry for more, and with aggressive fish, you can only have certain ones for certain sized tanks. The best sized tank is a 180, and i just get by with my 120. But in reality, the ebst place to keep fish is indeed the ocean. Just my 2 cents...