Look at Botia Loaches. Red Tails or YoYos. They are tough & durable scavengers. Neither will directly eat algae, but will thoroughly clean up the bottom, which in turn will limit nutrients available for algae growth.
Here's a pick of one of my Red Tail loaches aka Y. Modesta Botia. They look a lot like Red Tail Sharks, but are far more benifical. Great scavengers.