Hey PoolNewbie2006,

Wow. I can't imagine why you need so much acid. How big is your pool? You might have a problem with your test method. I'd look for verification of that. Make sure your acid is a good strength as well. Yours might be 14% or even less. I'll bet one of these things is your problem.

I would add more than 1/3 gallon if I had to. Just do it slowly in front of the return. It's getting diluted quickly.

I've been using a metal brush. It honestly hasn't done much more than the nylon one so far. It certainly can't hurt.