Altho it SOUNDS like a big tank, you need to realize that a 75 gal tank is NOT considered a large tank by any means, but you keep asking about "large-tank" fish to put in it...there's that research thing again. What you need to consider is adult size of the fish, their swimming habits, and aggressiveness (which BTW, the smaller the tank, the more aggression will show up, typically speaking). A clown trigger can max out at about 20" in the wild, so figure about 75% of that for a captive fish (that still puts the fish at about 16"). FWIW, a CT should be in about a 125 gal.