Mustard Algae at Pool Open-Maybe Ammonia Problem??

aswims12

Member
May 21, 2021
7
MO,USA
Sorry for the long post, but I do not want to repeat last year! I would really like to actually enjoy my pool this year! Last year we had a huge battle with mustard algae, and thought we had killed it all before we closed our pool. Opened on Friday May 21. Water was clear, but the bottom was very dirty! Added opening chemicals, cleaned pool, added an initial 12gal liquid chlorine (10%), then 3gal twice a day for the rest of the weekend, 3 gal once a day on 24,25,26,27th. Water was clear, but you could still see the mustard algae settled at the bottom, and on the ladder.
On Friday 28th
pH-8
Alk-180
CH-120
FC-0.4
CC-3.4
CYA-0
Added 2lbs CYA over night Friday, and 4lbs the next morning to bring up to 40 as of 1:30p Saturday. Added 3gal acid during the day on Saturday, brought pH from 8 to 7, alk from 220 (Saturday Morning) to 110 (Sunday Morning). Saturday afternoon when under heavy cloud cover added 15gal initial dose liquid chlorine, then another 20gal over the course of Saturday evening/Sunday day. Friday night 3lbs oxidizing shock, Saturday night 3lbs oxidizing shock, Sunday night 6lbs Chlorine shock, Monday night 6lbs chlorine shock. No liquid chlorine added on Monday (no bleach or liquid chlorine available within 90miles of me at any location open). During these 3 days, vacuumed/brushed constantly to keep everything stirred up, pool crystal clear, no sediment on bottom. Monday night chemical levels
pH-<7
Alk-100
CH-130
FC-1.4
CC-0
CYA-40
Levels not tested this morning due to heavy rainfall, but pool is still clear, nothing on the bottom, however, I did see a couple of water boatmen in the skimmer basket when I emptied it, which I have not seen since Saturday afternoon! Is it because of the rain, or is the algae coming back? And should I try to bring the pH back up, or wait to see if it rises after the rain? And what can I use instead of liquid chlorine/bleach until I can find some (I was raised to never use anything except that). Any help would be greatly appreciated!
 

aswims12

Member
May 21, 2021
7
MO,USA
Adding, after reading about others being unable to retain FC levels, could this possibly have been an ammonia issue? Water was clear when I opened pool, but there was a lot of sediment at the bottom. I had a tarp-like winter pool cover, closed end of September 2020. My CYA prior to closing (I think end of August) was 55ppm. This is my second year being an actual pool owner myself, so I was not aware this was not supposed to decrease! Prior to this weekends chemical add, I added 4lbs CYA at open d/t level of 0, then another 2lbs on Tuesday (25th) because level was still 0. I don't know why I didn't see this as a problem, I guess I was more concerned with the constant loss of FC to even think about the loss of CYA.
 
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Texas Splash

Mod Squad
TFP Expert
LifeTime Supporter
Jun 22, 2014
33,819
Texas, San Antonio/Marion, South-Central Area
Pool Size
17888
Surface
Fiberglass
Chlorine
Salt Water Generator
SWG Type
CircuPool RJ-45 Plus
So there is a protocol to follow when we see CYA disappear and pH drop, but it will require a lot of chlorine. The dry powders won't do it. And in the beginning of the operation you will need a lot of it. The only way to perhaps circumvent the process a little is by exchanging some water, but you'll still need to do the following:

1. (No CYA yet) - Increase the FC to 10 with liquid chlorine and test again in 10 minutes. If it fell below 5 ppm, add chlorine right away back to 10 ppm and test again in another 10 minutes. Repeat this process until the FC shows clear signs of holding around 6-10 ppm.
2. Once the FC begins to hold, then add some stabilizer for a CYA goal of 30 and increase the FC to 12 and continue with the SLAM Process until you pass all 3 SLAM criteria.
 

aswims12

Member
May 21, 2021
7
MO,USA
I have already added a total of 75 gallons of 10% liquid chlorine in the last 8 days, and still only have a FC of 1. I did manage to maintain a CYA from Saturday-Monday of 40, but that was after adding 6lbs CYA at the beginning of the week, then another 6lbs on Friday/Saturday, but I have not been able to add any liquid chlorine since Saturday PM since it is sold out everywhere. I did have cal-hypo shock at home, and added some Sunday night and Monday night so my FC would not disappear, but I also used that whole box up and can not find anymore. We did have a restock of 7.1% bleach that I am going after when I get off work. Was just curious if that was the cause of the pH drop, and what I need to try to do to correct the problem (other than SLAM) if it is from ammonia.
 

Texas Splash

Mod Squad
TFP Expert
LifeTime Supporter
Jun 22, 2014
33,819
Texas, San Antonio/Marion, South-Central Area
Pool Size
17888
Surface
Fiberglass
Chlorine
Salt Water Generator
SWG Type
CircuPool RJ-45 Plus
If you have ammonia, the CYA is only feeding it and making it worse. With all that chlorine, I suspect you didn't test every 10 minutes and reattack in 10 minutes to maintain the FC of 10 correct? Ammonia will eat all chlorine if allowed to drop. It is a very aggressive situation that requires aggressive testing and re-application of chlorine at very frequent intervals.
 
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