My first Condi did that; shrinking and expanding, and I think the problem with mine was that I fed it too much and being the new guy in the tank, it was really stressed out. It eventually died and my replacement one is doing great-it moved to the highest point on the LR in my 55gal and has stayed there for the past 4 months or so and seems happy. I feed it sparingly, maybe once every 2 weeks or so. Regarding your other post about lighting-I have T5 HO (6x54W) and the condi seems tothrive on it!