Slightly cloudy with brown residue at the bottom

Since I found this wonderful forum almost a year ago I've been following the BBB method and it has really been great! Most of the time the pool is very clear and my costs are low to maintain it. I use the Taylor K-2006 kit for testing. I added Borax to help prevent alge last year. I don't shock weekly like I used to since I've learned here that it's not necessary.

My setup is a 36,000 gallon vinyl pool with a Hayward 1.5 hp pump (I know, it's oversized) with a Hayward sand filter, and a Tri-chlor feeder.Here is a typical reading of the water over the last couple of weeks:
FC: 7
CC: 0
PH: 7.4
CYA: 55-60
TA: 150 (well water is high)
Temp: 90°

My problem is that the water occasionally looks cloudy in the deep end. I especially notice it after brushing (try to do this weekly). After a few days to a week it clears up. Also I constantly have some brown residue at the bottom - mainly on the edges and corner. I know this is dead alge - possibly mustard alge. I've been dealing with it by vacuuming it out to waste since it passed right through the sand filter. I've tried shocking it out last year but I may not have done it right. Also I am vigilant and make sure the chlorine levels never drop below the minimums so I'm not sure how alge could have gotten in.

Any suggestions on what I should do would be appreciated. Thanks!

Try and capture some of it when you vacuum. Maybe fill a bucket with the waste as you vacuum. Let it settle and try to smear a little of it on a white surface. If there is any green or yellow to it, then it probably is an algae.

Have you been noticing an abnormal usage of chlorine? Perhaps you should temporarily shut off your feeder and dose by hand for a weekend to check your demand.

I collected some of the residue with an ear bulb thingy and placed it in a jar. When it settled I poured the water out and took samples. I placed these on paper and attempted to smear them. It looked brown and the texture of sand. I suppose it could just be sand from the filter or dirt that made its way into the pool. Is there anything else I should check?

What about the cloudiness that we sometimes see after brushing?

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Originally Posted by proximo

I collected some of the residue with an ear bulb thingy and placed it in a jar

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Good thinking!

Filter sand should be quartz (unless you've got some sort of filter goop in your filter). With a digital macro photo OR under a hand lens, you should be able to see if the sand particles are quartz bits and crystals. Also, if you put bleach in the jar -- if it 'dissolves' or lightens the particles overnight, it's not real sand.

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What about the cloudiness that we sometimes see after brushing?

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What sort of pool surface do you have? Painted concrete? If so, it's just epoxy chalking (that's how it wears!).

A couple of days ago the cycle repeated. I came out and noticed a yellow film covering most of the bottom of the pool. We brushed the sides and bottom (it's a vinyl pool) and again got a very cloudy pool (can't see the drain in the deep end). Water looks yellowish. I'm running the filter constantly to try to clear it up. Also went ahead and raised chlorine levels to shock values (20) and cleaned behind the pool light (it was really gross).

Just can't figure out how algae is getting in there since my chlorine levels are consistent. I suppose this could be mustard algae rearing it's ugly head. Any other ideas I should try?

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.

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Originally Posted by proximo

A couple of days ago the cycle repeated. I came out and noticed a yellow film covering most of the bottom of the pool.

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Yes, mustard algae.

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Originally Posted by proximo

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.

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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.)

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.

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.

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.