Harlequin rasboras, black phantom tetras, or, for something larger and active, cherry barbs. BTW, you mentioned your tank doesn't have enough algae for a pleco yet? Even if you think it does, give him algae waffers and the occasional treat of live/fresh foods. He wont survive off the tiny amount of algae in your tank - especialy when he getting big. It's also reccomended you get a piece of driftwood for the pleco...