it's a strange question, but i've had my rbp's for 2 years and have never seen them poop, nor seen poop at the bottom of the tank. I've been raising different fish for over 20 yrs. and have always seen them poop or seen the poop at the bootm of the tank, but never my p's. It must come out like liquid. I only feed them catfish nuggets. Has anyone else noticed this??