will they eat this?

they will eat it fine if you just drop it into the tank.

As the disc soaks up water it breaks apart and they eat it just fine. Don't worry if they don't eat right away, some cories may avoid food when introduced to a new tank, or they may not be familiar with algae discs. After a few days they will figure it out. Try putting the disc in after you turn off the tank light, they may be more likely to eat then than during the day.