I have to agree with reefrunner, on this one. If you choose any tang for a 75, you should select one of the Zebrasoma genus (excluding the sailfins), or the Yellow eye tang (C. strigosus). Also keep in mind that purple and scopas tangs are notorious for becoming extremely defensive of their tank once established. Hippo tangs are large, active fish and definitely not a good choice. Mine has gone from the size of a quarter to over four inches in just under two years. Looking at him now hes beginning to make my 180 look small, and I regret purchasing him. A final thing to think about is that surgeonfish need a varied diet including large amounts of vegetable based grazing matter daily (seaweeds, macroalgaes etc.) and can put quite a large bioload on a tank with the addition of these foods. Please reconsider adding two tangs, it is really just not large enough IMO
, and their is a huge variety of interesting, colorful fish that are better suited to a tank that size.