the can eat it off anything, jay. They have done so in my tank. Make sure though that the plant in question isn't in danger of dying before they get to it. I had to push mine to eating it though when I first got them because the tank went about of month with them in it and not touching it. I put the tank in shut down, did everything as I normally do with lights and all except I didn't feed them for a couple days, maybe 3. After that, continue to feed the tank as normal, don't overindulge because of the 3 day no feeding. Soon, you will begin to see them making a change.