Chronic mustard algae problem

stephp25

Member
Jul 4, 2020
24
NY
i have been reading up on the reasons for your recommendation of using liquid chlorine instead of chlorine tabs. We have been using the tabs in an inline feeder. We had a pool leak and were adding water daily, so we have never had an issue with the CYA rising. We have fixed our pool leak so I recognize that it could potentially become an issue. We obviously do not want to do anything that would cause the algae to reappear. My question is, for pools that are open May-Sept. and are partially drained in the winter, is this a concern? Could we continue to use the tabs this summer, monitor the CYA weekly (CYA level is below 30 now) and if it does not become an issue before the end of the summer, see what the level is after partial drainage and refill next May and make a decision about the need for using liquid chlorine then or are there other concerns? I’d like to avoid the expense and hassle of switching over if that is possible but don’t want to have algae growth either.
 

mknauss

Mod Squad
TFP Expert
Bronze Supporter
May 3, 2014
43,661
Laughlin, NV
Pool Size
6000
Surface
Fiberglass
Chlorine
Salt Water Generator
SWG Type
Pentair Intellichlor IC-40
Sure, remember to keep your FC level based on the FC/CYA Chart. Tablets alone will not keep the FC at a high enough level. Also, tablets are very acidic, so monitor pH and TA more often.
 

stephp25

Member
Jul 4, 2020
24
NY
That’s a good reminder about adjusting the FC as the CYA changes. We actually have had the issue with the TA and pH being too high which is strange given that the tabs are acidic. I will keep an eye on it. I will always have the liquid chlorine on hand if I need to raise the level but just would prefer not to be dumping it in as the main source of chlorination. Thanks.
 

stephp25

Member
Jul 4, 2020
24
NY
We decided to wait another day after meeting the criteria to end the Slam before raising the chlorine to the mustard algae level for 24 hours because we felt that we would have more time today to check the level more frequently and add chlorine.. So we increased the chlorine up to 18 last night (actually accidentally a little higher) and it was at about 18 ppm when I checked it 30 min ago. We did not check OCLT last night since we had already met the criteria. We did not have any visible algae yesterday and just a little in the one place on the pool floor on the day before that. This morning there were some suspicious looking spots on the bottom of the pool (but not the spot that we had seen before). It rained last night after we vacuumed and brushed the pool so it is possible that it was not Algae but we are not sure. It dissipated when we brushed it. Any suggestions on how to proceed? Should we keep it at the 18ppm level today or drop back down to 12 and see what it looks like tomorrow morning? Any suggestions are appreciated! Thanks and Happy Fathers Day if you are a father!
 

mknauss

Mod Squad
TFP Expert
Bronze Supporter
May 3, 2014
43,661
Laughlin, NV
Pool Size
6000
Surface
Fiberglass
Chlorine
Salt Water Generator
SWG Type
Pentair Intellichlor IC-40
If you are passing OCLT you can let it come back to Target range and maintain it there. Remember, if you believe you had mustard algae, the target is 20% of CYA for a while.
 

stephp25

Member
Jul 4, 2020
24
NY
We have only done about 14 hours of the mustard algae shock after the slam so I assume we should finish that 24 hours and then let it drop to our target range. Correct? I just don’t want to stop too soon (if it was algae his morning) and have to start over again because it has been disappointing to be without the pool for 6 days!
 

mknauss

Mod Squad
TFP Expert
Bronze Supporter
May 3, 2014
43,661
Laughlin, NV
Pool Size
6000
Surface
Fiberglass
Chlorine
Salt Water Generator
SWG Type
Pentair Intellichlor IC-40
I assume we should finish that 24 hours and then let it drop to our target range. Correct?
Correct.
Up until the pool was in Mustard Algae SLAM levels, it was perfectly safe to swim in, as long as you could see the bottom of the pool.
 

stephp25

Member
Jul 4, 2020
24
NY
I don’t understand how this is possible because we have done everything by the book. We finished the mustard algae shock last night and even made sure that the level was still at 18 in the evening because that’s when we first started it the. Ishtar before and figured that it would benefit from being elevated overnight also. Thia morning there’s definite algae in the corner where we have been seeing it. How is this even possible? Where did we go wrong? This has been like a full time job for me this past week as I checked the chlorine levels and added chlorine many times throughout the day. We slammed it for five days and then did the mustard algae shock level on the sixth day and the chlorine level is still at 12 P PM. How could algae have grown when the chlorine level was 18 Overnight? To top it all off, the previously mentioned pool leak seems to be back after spending a tremendous amount of money fixing it. Is it possible that the high chlorine level caused another issue at the joint right behind the return line? I am so discouraged. I don’t understand how we have the only pool that has mustard algae that is just resistant to absolutely everything. Any help is appreciated. Thank you!
 

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mknauss

Mod Squad
TFP Expert
Bronze Supporter
May 3, 2014
43,661
Laughlin, NV
Pool Size
6000
Surface
Fiberglass
Chlorine
Salt Water Generator
SWG Type
Pentair Intellichlor IC-40
If the FC levels are not managing it, is it possible to do a healthy water exchange to fresh. Something is not right, and if testing is accurate and chlorine additions have been done to the proper levels, then something is in the water that we do not know about.
 

stephp25

Member
Jul 4, 2020
24
NY
Do you mean to drain the Whole pool? That would be very expensive. What could be in the water and is there a way to test for those things?
 

mknauss

Mod Squad
TFP Expert
Bronze Supporter
May 3, 2014
43,661
Laughlin, NV
Pool Size
6000
Surface
Fiberglass
Chlorine
Salt Water Generator
SWG Type
Pentair Intellichlor IC-40
That is the problem. What testing data you have given says you should not have this problem. So it is something that cannot be tested for.

A healthy water exchange of 50% may help. No guarantees.
 

stephp25

Member
Jul 4, 2020
24
NY
Also I am sure that the readings were accurate. I managed a commercial pool for years so I am very familiar with doing pool readings. I often did it twice to make sure it was accurate.
 

stephp25

Member
Jul 4, 2020
24
NY
Sorry but I have another question. Yesterday and today, there was black sand-like substance floating in the skimmer. It almost looks like a spice floating on the surface in the skimmer. When I stick my hand in, it gets on my hand. I don’t see it on the water surface in the pool itself. Any idea what this might be?
 

mknauss

Mod Squad
TFP Expert
Bronze Supporter
May 3, 2014
43,661
Laughlin, NV
Pool Size
6000
Surface
Fiberglass
Chlorine
Salt Water Generator
SWG Type
Pentair Intellichlor IC-40
If it is floating it could be decomposed suncsreen, hair products, etc. Is it grainy or greasy?
 

stephp25

Member
Jul 4, 2020
24
NY
If it is floating it could be decomposed suncsreen, hair products, etc. Is it grainy or greasy?
No, we haven’t been in the pool for at least 10 days so I don’t think that is it. It is not really greasy. It is more sandy. It almost looks like sprinkled Oregano (but is more black than green).
 
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