Most blennies rely on algae for the main part of their food (at least the ones that usually make it into the aquarium trade). Most of those will also take anything else that is offered (I don't think any are strictly vegetarian), and there are some that we get that don't eat algae at all (years ago I bought a group of 4 little blennies that looked like the "lawnmower" blenny as they are now called, but these little guys didn't touch algae, they preferred to take shrimp and squid away from a little cat shark that I hatched in my tank. Kind of funny to see a blenny stealing food out of a sharks mouth, literally.
You can usually tell what something eats by the shape of their mouth. Take a look at your redlip blenny, it should have a mouth that looks a lot like a Kole Tang's mouth, large with big lips. Their mouths are made for scraping algae off of rocks. If you have any algae on your glass, look for lip prints on your glass from your blenny. It'll look like a little tiny woman wearing lipstick has been puckering up to your glass.
[ October 28, 2001: Message edited by: davelin315 ]</p>