I wouldn't think it would hurt his health much. Fish like people taste things, and at one point it would seem he got a mouth full of the spinach cube. He must have liked what he tasted. As long as he is eating, I wouldn't worry about it. The worry comes when they stop eating. I have always wanted to try a tire track since they have really nice patterning. I have my spiney fire eel though and would be hard to do 2 monster eels in the aquarium I have. They really are splendid fish. My Cambodian in laws just love my fire eel... but I can't tell if they are watching him in amazement... or fantasizing about how he would taste.