In preparation for winter, I ordered a diaphragm kit for my air pump...thought I'd have a nervous break down doing it, but that's another story - LOL ! I visited the fish hatchery today to buy new air stones, but they only had two and I need four .....just not my day Anyway, they suggested washing a couple of the old ones, with muriatic acid, said that's what they do. I also bought new hose, since they're a few years old. I'm reluctant to use the acid....seems kind of strong. Anyone have experience using it? Thanks!