So I'm changing my playsand out for peace river gravel due to problems with filters plugging and irratation on the bottom of the rays. I decided to do half at a time and found now that I've got sand on one side and gravel on the other all the rays lay on the sand side even tho I feed on the gravel side all the time. Has been like this for 2 weeks. Even the rays that had problems with disk irratation lay there. Do you think it's due to new enviroment or due to the fact that the sand feels more natual to them?