First fish

Evening everyone,

I am researching the purchase of my first fish for my reef tank. I have been looking into a few choices.

1. Sailfin/Algae Blenny, what type of algae do they eat?
2. Blue/Green Reef Chromis
3. Cardinal Fish

I'm looking for something that eats the flowing algae (looks like hair?), and a sand sifter to work with my substrate. I was looking at Tangs, but everything says 75 gal or more, is this accurate?