Cory catfish do npt eat algae. They are more omnivores with a lean towards protein. They lovee shrimp pellets, complete tablets and often will take to algae tablets, though I know of no cories that actually eat alage on plants. They can help keep alage low, especially on rocks, by moving things about. But I am sorry to say that if you bought them to keep your plants clean then that was not a wise purchase. Your fish store doesn't seem to know much about fish.
If you plan on keeping them then buy some sinking pellets for them. for 2 cories, 1 pellet a day will be more than enough. These fish also are much more active and fun to watch in bigger groups.
If you plan on keeping them then buy some sinking pellets for them. for 2 cories, 1 pellet a day will be more than enough. These fish also are much more active and fun to watch in bigger groups.