Hi, I have a 30 gallon talk for a 3-4 inch long pleco named Mr. Suck. I do a 50% partial change of his water weekly, and when I do I add Stress Zyme, Quick Start and Ammo Lock. He gets a white underbelly that comes and goes along with lighter stripes on his body that also come and go. I've checked the ammonia in the tank, it's at a good level. I know he isn't supposed to be this pale but I just can't figure it out. Does anyone know what's wrong with my poor boy? I've attached pictures for reference.