that is not entirely true. your theory basically means you could pepper spray a fish and they wouldn't feel any effectP0GS;3425477; said:Peppers are only spicy because we and other mammals have capsaicin receptors as well as taste buds. Peppers evolved the spicyness (capsaicin) to prevent grazing animals such as cows from eating them. Birds do not have these receptors which is why you will find hot chilis in parrot food. As for fish, since they have been around longer than pepper plants have I would assume it would be fine to give your pleco green and other bell peppers.