Quote Originally Posted by proximo View Post
A couple of days ago the cycle repeated. I came out and noticed a yellow film covering most of the bottom of the pool.
Yes, mustard algae.


Quote Originally Posted by proximo View Post
heavily covered by brown residue. Still scratching my head as to how this could have happened! I have kept chlorine at ~7ppm for weeks with the chlorine feeder.
1. Read the Best Guess page linked in my signature. If you don't know your CYA level, you can NOT know what "shock" level really is. Having used a feeder "for weeks" would suggest it may be very high.

2. Don't brush algae unless the chlorine is VERY high. Doing so with mustard algae can turn it into a green algae bloom. Before you brush, make sure your chlorine levels are at Best Guess shock levels . . . THEN, add 5 gallons of PLAIN Walmart bleach immediately before brushing.

3. Lemme say it again, a little differently. Unless you use copper (stains hair and pools) or "Yellow Out" type products (screws up your pool chemistry for weeks), the ONLY way to control mustard algae is to follow Best Guess levels. If you follow pool industry recommendations, you're gonna get used and abused by the pool stores! They LOVE mustard algae.

4. You *can* swim at Best Guess shock levels. Skin is very, VERY chlorine resistant. Just don't wear new fashion women's suits (they are the LEAST chlorine resistant) and don't dunk perm-ed or dyed hair in the pool. (In other words, if you skinny-dip and keep your head above water, you'll be fine.)