If your looking at a black volitan, your going to need a 150+. Those things get big and need room to move around. You also don't want to have too small of a tank because it could sting your other fish, if not eat them. You can get them at most every store year round. They do tend to sell quick, especially in the small sizes.

If I were you, I'd look into getting a lion that grows no larger than 6-8", only if your going to have it in a 75 from the start.

I am looking at the fu manchu lion since it only gets about 4" long. You may want to consider that as an option.