Ya... This is a problem I had in the past. I actually had 9 discus fry in a 55g and they didn't do well. I ended up losing the whole lot of them. Im not sure if it was due to a bacteria or if the tank was to big and they didn't feel secure enough to come out and eat or if it was to gas bubble disease. This is going to be my second time trying to grow fry and I'm starting with the 20g and working them up as they get bigger. Luckily the fry we got for this challenge are already a good size to start wth. I've also found with some of my other discus is that if its bare on the bottom they didn't feel comfortable... I think its because they didn't have a sense of the "bottom" of the tank? who knows.. lol. but they are definately skidding fish so putting something on the sides will help them from seeing to much outside of the tank.