A schoool of 4 or more of corydoras was be a great clean up crew. You could also do some species of loaches such as, zig zag loaches, chinese loaches, skunk loaches. Neon tetras would be a good schooling fish. You could do harlequin rasboras or scissortail rasboras. You could have gold barbs, cherry barbs, rosy barbs. Another good schooling fish would be zebra danios but they get a bit nippy. Platies would be a beutiful addition to your aquarium.