they will eat decaying plant matter, but will not touch the live plants. their mouth parts are not sophistocated enough to eat through the cell wall of a plant. they love brown algae, and will eat green slime algae. if they run out of that, you have to suppliment their diet with blanched veggies (blanching=putting zucchini, green beans, romaine lettuce, cucumber, etc. into a small cup of tank water and nuking it for a minute or so) blanching starts breaking down the cell wall of the veggie so the otos can eat it.