i nabbed a couple of foxface rabbitfish from my lfs back in december. theyre excellent for green hair algae. your mileage may vary.
BUT, i don't necessarily think this is your best option, as it will introduce more fish and fish waste into the system, which might cause more algae to grow. unleashing typical cleaners in a tank with a trigger is like presenting the trigger with a buffet.
I keep a blue-angle in with my triggers, he pretty much keeps all but the shortest of the hair-algae at bay (angain with more fish waste). For the substrate I keep a daimond watchman goby. It is feisty enough to hang with triggers, and keeps the bottom spotless, consitently siftng and picking out bits of food.