I know salt and fresh are very different, but I am questioning the quality of the pool sand. I have heard that silica sand(made from glass, mainly what you might find in non-tropical beaches) can release toxins in aquariums. Also, if this sand has any clay or otherwise contaminated content, can harm your tank/fish. Just my $.02. I can't say for sure what is in pool sand or how it would affect your tank, just bringing up possabilities.