It can't produce any more waste than the amount of food that you feed it.I have never even seen my knife's poop but of course it does because it eats at least once every day.
Mine poops about as much as any other fish would. They can be messy with pellets, but other than that, they're no pleco. He's about 20 inches, so his poop is big and easy to clean off the sand. And if you feed massivore, the poo is the same color as the pellets.
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