I saw down after work in front of my tank and watched my ray cruise the tank as normal. When he climbed the glass, I noticed that his underside was a reddish pink about 1-2" from the edge of his disk. Is this normal, or is my gravel irritating his bottom? I'm doing my first waterchange tomorrow morning and will remove the gravel if thats whats causing it. If it's normal, than don't mind me. 
