fishy fish fish

So my blue gourami died, and turned out my other 2 gouramis had been fin nipping it - and looks like they may have killed the other tetra too. So what have I done to rectify my little tank bullying problem? I bought a shark! :) He's 5 inches long and looks like he has a hammer head, although I must stress he is not an actual hammerhead! So far the gouramis are hiding, and peace has been restored.