Actually they are in there as stand-offs for the egg crate diffuser floor (I ran out of marrets). there's only about a total of 1' to 1.5' copper. I think I remember looking into it and they are bad only for invertibrates or when they are in their ionic (liquid) state. I think they are stable in their solid state. Any way I still coated them with epoxy to seal them from the water.paulW;1936698; said:I haven't read the entire thread, but you don't plan on leaving the copper pipe bits in there, do you? Copper is toxic to freshwater fish.. I mean, I assume you knew that, but I figured I'd point it out just in case.