Algae Won’t Go Away-Mustard Algae

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K

Kylum

Member
Mar 17, 2022
6
Ft Worth
Hello,

So last Tuesday I noticed a few small patches of algae in our pool. I immediately started the slam process. Every morning the same spots have reappeared and continue to loose chlorine over night. The sun has been brutal here in the Dallas area this past week and will continue to be relentless. With CYA being at 40 I’m slaming at 20 to help with loss from the sun during the day. My wife has been adding chlorine during the day while I’m at work. She refuses to test and measure (I’m not going to win that battle) she dumps half gallon every two to four hours as she can between work. FC has not been below 16pmm during all my checks. Now about 3 days ago I’ve bumped the FC lvl to 25 thinking it might be mustard algae, but letting it drop to 16pmm towards the end of the day because the wife and kids refuse to not go swimming and when done I boost it back up to 25pmm or higher. Brushing and vacuuming takes place at least twice a day.

During this process I have had two days where there was zero overnight chlorine drop but not back to back and not this morning. Note: the pool has been crystal clear this whole time with minimal algae spots on bottom and 0 to .5 CC the entire time as well. Sand filter/ pump has been running 24/7 and backwashed daily weather needed or not. I’m loosing my mind and patience please help?

We have used 10+ gallons of Pool Essentials 10% LC at this point and don’t want to blow through 12 gallons I have over the next week.

TF100 results prior to SLAM
FC - 7
CYA- 40
PH- 7.7 lowered to 7.2 for SLAM
TA -70
CH - 135
 
Last edited:
I assume you read the Mustard Algae article in Pool School. Have you checked for signs of algae in all possible hiding places?

"While at mustard algae shock level you need to thoroughly brush the entire pool, including walls, floor, steps, skimmer, under ladders, everywhere. All pool tools and toys and anything else that is used in the pool needs to be wiped down with a dilute bleach solution or soaked in the pool for an hour while at mustard algae shock level. Bathing suits should be run through the laundry. If you have underwater lights, they should be removed from their niche and the niche brushed out, and then the lights replaced. If you have fountains, or waterfalls, or other water features, they need to be run for at least an hour while at mustard algae shock level. Be very thorough, or you will most likely just need to do it all over again."​

Is the algae you're seeing on the bottom dead (like dirt) or does it require brushing to remove? If it swooshes away it's probably dead algae and sign the SLAM is working.
 
Rancho Cost-a-Lotta said:
I assume you read the Mustard Algae article in Pool School. Have you checked for signs of algae in all possible hiding places?

"While at mustard algae shock level you need to thoroughly brush the entire pool, including walls, floor, steps, skimmer, under ladders, everywhere. All pool tools and toys and anything else that is used in the pool needs to be wiped down with a dilute bleach solution or soaked in the pool for an hour while at mustard algae shock level. Bathing suits should be run through the laundry. If you have underwater lights, they should be removed from their niche and the niche brushed out, and then the lights replaced. If you have fountains, or waterfalls, or other water features, they need to be run for at least an hour while at mustard algae shock level. Be very thorough, or you will most likely just need to do it all over again."​

Is the algae you're seeing on the bottom dead (like dirt) or does it require brushing to remove? If it swooshes away it's probably dead algae and sign the SLAM is working.
Click to expand...
Yes, I read through the mustard algae article. Everything has been scrubbed well and disinfected. However, I did forget the skimmer door, but earlier today I redid the entire skimmer. Ladder was washed down vigorously with CL2 solution and then pressure washed and scrubbed again not going back in the pool until the family started trippin about swimming again. All algae, even from the start appeared dead (dirt like) and easily wished away(brushed like heck anyway daily).

Update:
I decided to check CYA because I wanted to bring it up a little cause of the Texas sun being brutal and I could still make out the black dot up to the top. CYA pretty much disappeared some how or at least between 10 and 20. I’m guessing due to backwashing and vac to waste plus topping water off.

This brought up another question. It dawned on me that the two days I passed my OCLT test I believe were the nights I did not add any water after backwashing/ vac to waste. Yes, OCD about backwashing for some reason. Would one see a drop in FC over night while the FC and municipal chloramines are commingling and balancing out?
 
Ok , so it looks like I might have found the culprit to my algae problem. I’ve been slaming at 25-30ppm for several days since I was thinking it was mustard algae and it is a yellowish color so I’m still not 100% sure. Nothing at all has been in the pool not even ladder and it keeps coming back every morning and failing the OCLT. I’m off for a an extended weekend and decided to vigorously check all the seams in the liner and found a seam that was not bonded fully from factory and it was full of algae. It right where it begins to go vertical at the wall. Going to have to invest in a snorkel to keep this clean cause it was a pain in the butt!!!
 

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