Mustard Algae - Help!

[spbb05]

First off, Thanks for the site! I filled out the pool info sheet. I also did FB and twitter.

I'm having a big problem with yellow algae. It stated a month or two ago with small spots and I was just able to brush it away. It got the point last week where all the walls, bottom and steps were covered. The algae brushes off easily and is like a powder when brushed. I have peen using a pool store for water tests. I ordered a Taylor K2006 today.

Brief History - I have used kept my pool pretty will balanced by pool store standards. I took your advice several years ago and use baking soda and borax instead of their products. I also use the Quat you recommend and don’t use other additives. Due to budgets, I skimped on Borax and quat most of last year and this year.

I started asking questions this summer and my CYA is over 100. In the 10 years at the house I haven’t done a water drain/refill. I'd like to do one this winter. I use cal hypo 73% as shock and have also used bleach in the past.

So my question is - Where do I start? Do I drain and then deal with the algae later or attack the algae first?

Thank you!

[PoolDoc]

Hi Spbb . . .

1. Some pools are more prone to mustard algae than others, but I don't know why.

2. High CYA is *usually*, but not always, a contributing factor.

3. High chlorine will kill mustard algae, but with the CYA levels over 100 ppm, it will take extremely high chlorine levels -- higher than 20 ppm. Read the Best Guess page linked in my signature.

4. Polyquat is not, in my experience, very effective against mustard algae. Copper can be, but at the price of stains and green hair.

5. Sufficiently high levels of borates (> 50 ppm) seems to inhibit mustard algae.

6. Very low levels of phosphates (> 125 ppb) probably weakens mustard algae significantly. I'm currently testing this, and seeing positive -- but not definitive -- results.

My recommendations for you:

1. Add large doses of bleach in the evening, after brushing. 2 gallons of 8% plain household bleach per 10K gallons of water.
2. Maintain chlorine levels above dark yellow via OTO testing, till your K1006 arrives.
3. Post your test results, as soon as you have the K2006. Then, let's decide what to do.

[Phillbo]

What about draining and using a pump up sprayer to spray the areas with bleach and let dry .. If it dries out it will die, right?

Or will it just come back again once refilled?

[PoolDoc]

It's not that hard to kill mustard algae, once the pool is drained. Spraying bleach is not a bad idea for black algae, but it's overkill for mustard algae. Mustard algae does NOT penetrate into the plaster. Simply spraying it off with a hose nozzle, as the pool drains, is more than enough.

[chem geek]

Yellow/mustard algae prefers shade so will tend to hide out behind light niches and under removable ladders. So even if you replace the pool water, you need to get into those areas and thoroughly kill off the algae or it will come back after you refill the pool unless you maintain higher than usual chlorine levels. It's best to eradicate the algae if you can.

[spbb05]

Thank you all for your responses. I apologize for the delay in answering. I thought I had email notification set up and apparently did not.

I expect the kit to be here by Tuesday or Wednesday. I've brushed a few times and it is only coming back only in few spots and in smaller areas. I've also used 3 gallons of 8% 2x times since posting. I'll report tests as soon as possible.

Any hints or tips on using the the test kit for the first time user?

[spbb05]

The K2006 test kit arrived and the results are:

FC - 11.5
CC - .5
PH 7.6
TA 150
CH - 280
CYA -100+ - the black dot disappears at the top of the letters CYA on the tester.

[PoolDoc]

Sorry for the slow answer.

With FC > 11 ppm, you may have regained control of your pool. If not, do this:

1. Retest your CYA, using a 50:50 dilution of pool water with tap water. Multiply the results x2 for your actual CYA level

2. Read the Best Guess page, linked in my signature, or found here: http://www.poolsolutions.com/gd/best-guess-swimming-pool-chlorine-chart.html

3. Adjust your chlorine level upward to an appropriate level.

4. Stop using stabilized chlorine (trichlor or dichlor) and use only bleach. with CH = 280, you probably don't want to use calcium hypochlorite either, though there is a way to do so IF (a) you have a sand filter, (b) a working skimmer, and (c) can make SURE that any chlorine feeder located upstream of the filter is EMPTY.

[spbb05]

Thank you Ben. The pool looks a lot better and I'm not seeing any more algae.
I retested the CYA as recommended and its 160.


I have more questions about stains/calcium build up on the floor and doing a partial drain to drain reduce cya and CH.

Can I ask on this thread or should I start a new one?

Thanks again!

Steve

[PoolDoc]

+ Stains should be a separate thread.

+ Your CH level is not necessarily a problem; don't drain because of that.

+ Your high CYA is not necessarily a problem; it can actually make winter maintenance easier. Once your pool is algae free, you'll may be able to add chlorine just 1x per month.