discus eating feces

[merk]

I went away for two days and when I came back, there was no waste in the bottom of the tank. I'm assuming the discus ate it. Can this harm the fish?

[judy]

It's possible they did, but not very likely. More likely, if they were not fed while you were away, there would be no feces produced.
Or, if you have your biofilter functioning properly, any waste may simply have been broken down by your friendly neighbourhood nitrifying bacteria gang...