with a lion, you are'nt gonna want a lot of big fish, but maybe a koles tang, they are only @6 or 7 inch, and do eat algae, or else a lawnmower or algae blenny, they wiil also help with the algae, other than that, thereis not alot that youcan put in with him, that won't be lunch, being as you have a 75 gallon, maybe an emerald crab, if you can find a big one for sele, because the ony problem with a lion is that they will eat LETERALLY everything they can fit in their mouth
HTH