Are you using the spill-over feature often? If so, it could be exacerbating your pH problem. Anything like fountains, spill overs, jets and the like will cause a pH rise from the aeration they provide. Nice to use when you *want* to raise your pH, other wise..... well...<shrug>
Definitely switch to muriatic acid. It is cheaper, faster, and doesn't cause a build up of sulphites like pH down does when used often.
Definitely switch to muriatic acid. It is cheaper, faster, and doesn't cause a build up of sulphites like pH down does when used often.