Slime behind Niche Light

[chem geek]

When I have very infrequently removed my pool lights I typically find yellow/white paper-like crud that breaks apart easily. It's probably white water mold though as Ben points out biofilms are colonies with many different bacteria and even other microorganisms. Circulation of the water in pool light niches is very poor so chlorine gets depleted there and all kinds of organisms can grow. That's one reason why it's very important to always maintain a minimum FC/CYA level in a pool since there are sources of potential pathogens available wherever circulation is very poor, though in practice it's mostly a source for where algae would develop again, especially for yellow/mustard algae. Thoroughly and completely decontaminating the niche may help, but it's almost impossible to ensure that you kill absolutely everything there. Nevertheless, it's one of the steps in trying to rid a pool of yellow/mustard algae and it sometimes works.

[selectstar]

Thanks for the input. Some pics to show what I have been dealing with, just FYI.
Last season before close.



After opening niche light a few days ago.

[PoolDoc]

I'll post more later . . . but chlorine smells almost always mean you do not have ENOUGH chlorine, so the chlorine can't stay ahead of the dirt.

Do this:

1. Run your filter on high 24/7, if you aren't already doing so.

2. Purchase a local OTO/phenol red drops kit (yellow/red drops). Use it to maintain chlorine levels; you want to reach OTO 'orange' (12 - 20 ppm).

3. Also purchase 6 gallons of plain store brand 8% household bleach . . . for EACH 10,000 gallons in your pool. Begin adding 2 gallons per 10K each evening.

4. Order a K2006 testkit (testkit page with Amazon links from my blue signature block below). Test your pool once you receive it.

5. After you get your OTO kit, tell us what your pH level is.

[selectstar]

Do this:

1. Run your filter on high 24/7, if you aren't already doing so.
Yes. 24/7 for a over a week now.

2. Purchase a local OTO/phenol red drops kit (yellow/red drops). Use it to maintain chlorine levels; you want to reach OTO 'orange' (12 - 20 ppm).
I have what I think is the OTO, when I last tested yesterday it was orangish brown

3. Also purchase 6 gallons of plain store brand 8% household bleach . . . for EACH 10,000 gallons in your pool. Begin adding 2 gallons per 10K each evening.
I was wondering adding more chlor would be necessary. I will try this tonight

4. Order a K2006 testkit (testkit page with Amazon links from my blue signature block below). Test your pool once you receive it.
I have this kit. See image. Before shocking, ph was about 7.1-7.2. Now it is low. Is this due to using the powdered bag shock?





5. After you get your OTO kit, tell us what your pH level is.
Appears to be lower than 7

[PoolDoc]

+ Here's an approximate OTO chart, for off scale results:



It sounds like your chlorine may be in the 30+ range; if so neither your pH nor DPD chlorine test results will be valid.

+ The test block you photographed is from a K2005 kit, not a K2006. You need a K-1515 kit to make up the difference.

+ Please test and report your CYA (stabilizer) level.

[selectstar]

My k2005 says cya approx 100. the test strips say approx 40-50. I've tested each twice with same result. My cya was about 80 last season before close. Upon closing I drained about a 1/3. I cannot see how it could be 100 per the k2005. I have not added any CYA. I did add the bleach as instructed last night. The smell of the water seems to have dissipated, but clarity and overall quality is still suffering. I did do the diluted test via k2005 a couple times before adding bleach.

1st go chlorine off the scale
2nd go with half/half dilution looked to be off scale but close
3rd go with .25 and .75 dilution looked to be about 2ppm

after bleach this morn
1st go chlorine off the scale
2nd go with half/half dilution looked to be off scale but close
3rd go with .25 and .75 dilution looked to be about 4-5ppm

Am ordering the k1515 but this is the best I have for now.
Again thanks.

[PoolDoc]

The smell + the difference between your OTO results (>20 ppm) and your DPD results (~16 ppm) suggest extremely high combined chlorine levels. Do this:

1. Check your pH using the test in the K2005. But, first do a 50:50 dilution with DISTILLED water. The pH result does not have to be adjusted, but read it quickly. The phenol red in the K2005 is compensated to ~10 ppm TC, or 20 with the dilution, but your TC may be higher than that.

2. If your pH is below 7.8, add borax, a box at a time, till you reach ~8.0.

3. Then, begin adding bleach -- but first tell me how many gallons you have OR what your the pool's dimensions are.