With my new set-up I only do 5 gallon water changes and use the white salt buckets to do it. Previously I'd used larger containers that were of various colors. But now I'm mixing it in a white bucket I'm noticing strange rust/brown colored residue that forms when the salt is mixed. Or is this only happening to me? The longer you leave the water mixing with the power-head, the more of it there is. What is this stuff?



