Slightly cloudy with brown residue at the bottom

[proximo]

Pool water still cloudy a week later so I'm going to try to keep the chlorine levels at shock level and the filter going until it clears. Floor is now 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.

[PoolDoc]

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.

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.)

[proximo]

Thank you for the reply, PoolDoc! So the next time I see a film on the bottom I will bring chlorine to BBB shock values THEN brush. Thanks for that great tip!

I DO know my CYA levels - see first post - 60-70 right now. I've been following BBB for almost a year and never use the goops form the pool stores. I use a combination of feeder and liquid generic bleach. That's why I'm confused because I thought by following BBB and keeping things within the proper values this would not happen. However, it's possible I never totally gotten rid of the mustard algae and that with the intense heat we've been having it was able to come back somehow. OR when my pool light came off for cleaning it exposed a ton of algae spores to the pool.

I'll keep it a shock values until things clear. It was clearer today but tons of debris on the floor to vacuum.

[PoolDoc]

Mustard algae is VERY resistant to chlorine . . . and most other things you might want to put in your pool. Using borax to raise borate levels to 60 ppm seems to make pools significantly more resistant to algae, including mustard algae. A 60 ppm borate level will NOT get rid of mustard algae, but it will make it easier to eradicate and less likely to return. It's a significant expense, but you only lose it from splash out and backwashing.

If you decide to do it, you'll need about 25 boxes of borax + 8 gallons of 31% muriatic acid. Add 3 boxes of borax, followed by a gallon of muriatic acid. Add the borax slowly, through the skimmer. Add the muriatic acid directly to the pool BUT read the muriatic acid guide, linked in my signature, FIRST. Wait 4 hours, then check your pH. Add either borax or acid to bring pH back into range. Then repeat, till all the borax is gone, and the pH is in a normal range.

[Watermom]

If your CYA is already at 60-70, you might not want to continue to use your feeder as it will cause your CYA to continue to rise.

[proximo]

Thank you, thank you PoolDoc and Watermom! I really appreciate your responses.

Last fall I did the Borax treatment you recommended here. Although the strip test I have isn't terribly accurate I think it's around 50ppm. I will keep raising it though as we may have lost some due to water changes.

I've kept the chlorine levels around 20ppm and it's crystal clear this morning! Just have a ton to vacuum out now off the floor. Would you keep the pool at shock values longer? If so how much longer to totally kill the mustard algae?

I may switch to liquid bleach as I dont want to raise my CYA anymore. I'm just afraid I'll forget a dose!

[nottapooltech]

How is your pool now? I am having basically the same problem. I am curious if you still have a lot of sediment/dead algae on the bottom?