Algae eating fish...wich one?

[coralmorphian]

The obvious answer would be a tang...BUT...

I have a 50 gallon, and I dont want to have a tang in a tank this small.

I do need to keep the macro algae in check though. I have a lawnmower blenny in there as well as a sixline and 2 bangi's.

As for other critters I have 2 cleaner shrimp and 2 crabs. 1 porcelin and 1 emerald.
2 fighting conchs 10 nassarious and 10 nerite snails.

What suggestions do you folks have for inhabitants to keep the algae growth down.