Fighting mustard algae I think. Have a few questions.

[John2]

So on May 28th I started battling what I believe is algae and possibly mustard algae. it was dark sand looking clumps that disappear temporarily when brushed and then come back. Now it’s a much lighter color. Here it is June 2nd and it’s still here although much lighter in color. So either I’m SLAMing wrong, or it’s not algae, just sand, or this process is going to take way more time and chemicals than I ever thought. When I brush the sand or algae off the bottom it turns into a cloud and disappears for a bit and then returns. So that means it’s algaIe, correct? I know i let the chlorine get down below shock levels a 2 times but not for long normally. I just wanted to let people swim without bleaching their swimsuits or causing other irritations. When I bought my pool kit, it came with zeosand, so that’s what I have in my filter.

I have the pool math app but once I started shocking and testing more often, I found it easier to record everything in my notes app as opposed to the pool math app. Every note that says I added shock was 68% cal hypo.

I know TFP is against using trichlor tablets but I have a bunch left over and it’s not raising my CYA level. Actually my CYA level has went down from 30 to 20. I assume this is because of how often I’ve added water to the pool after evaporation and a couple of backwashes.
When looking at poolmath screenshot, notice number of days ago those were taken. Some numbers were from 12 days ago. Also at that time I didn’t realize you couldn’t do in between CYA numbers so even though it says 25, it was most likely 30. I’ve read a few more threads about how to read CYA since then.
Here is a link to a video of my pool that I took today:

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My questions:

1. do you agree it’s algae not sand? If so, do you think it’s mustard algae?
2. (Assuming it’s algae) Even though the algae isn’t gone yet, wouldn’t I have killed off all the bad bacteria by now making it safe to swim?
3. If normal target FC is 4, shock level is 12 and mustard shock level is 18, then once I bring the FC above 18, how low can I let it get during SLAMing (especially during the day) before adding more chlorine? Do I need to keep it at or above 18? Or can I just bring it up to 18 and let it fall to 12 before bringing it back above 18?
4. Will an automatic floor vacuum that connects to the suction side be as good as brushing? If not, will it be helpful in between brushings?
5. Will moving to a higher chlorine level than listed on the CYA chart for mustard algae, speed up the process? I’d be okay with raising it to 25 or 30 if it’ll make the process go a lot faster and not tear anything up. So long as it’s down to safe levels for swimming this Saturday.
6. When washing swimsuits to get rid of algae spores, is there any special requirement or just use regular laundry detergent?

Here’s my notes:

May 28th
8:30pm FC = 14

29th
12:20 am FC = 12.5
10:20am FC= 8.0
6 swimmers from 2:30pm to 5:45pm
8:00pm FC= 4
Added 4LBS of shock (+15 FC)

30th
11:30 am FC = 9.5
Added 3 LBS of shock (+11 FC)
5:30pm FC = 12.0
6:15pm Added 2 LBS of shock (+7.6 FC)
10:15pm FC = 15.0

31st
1:30am added 2 lbs of shock (+7.6 FC)
11am FC = 13.5
Noon, added 3lbs of shock (+11 FC)
Added pool toys and hoses
Also adding water to bring water level up.
Sometime late afternoon, hooked up automatic vacuum after backwashing for 20 to 30 seconds.
11:45pm (still adding water but almost done) CYA = 20 FC = 12

June 1st
10:30am FC= 12
2:30pm FC = 10
7:20pm FC = 8.5
8 PM added 3 pounds of shock ( +11 FC) and turned off auto chlorinater (trichlor)
10:15pm FC = 18

2nd
5:05 AM FC = 16 (sunrise 5:33) so OCLT failed.

 

[Socojoe]

I too thought I had an algae issue because I get those piles of dirt/pollen/sand or whatever it is “stuff” on the bottom of my pool. It collects in pretty much the same spots over and over. I came to the conclusion it settles in those areas due to the circulation of the water in my pool along with liner seems and depression. I also did a overnight chlorine loss test which proved I didn’t have anything eating up my chlorine overnight because didn’t lose any chlorine overnight. I would suggest doing overnight chlorine loss test in order to rule out an issue in your water. Sorry, I noticed you failed the OCL test and I’m not much help.

 

[John2]

I too thought I had an algae issue because I get those piles of dirt/pollen/sand or whatever it is “stuff” on the bottom of my pool. It collects in pretty much the same spots over and over. I came to the conclusion it settles in those areas due to the circulation of the water in my pool along with liner seems and depression. I also did a overnight chlorine loss test which proved I didn’t have anything eating up my chlorine overnight because didn’t lose any chlorine overnight. I would suggest doing overnight chlorine loss test in order to rule out an issue in your water.

Thank you! Mine always collects in the same areas too but I thought maybe the algae is being circulated to the same spots. I did an overnight test last night and I lost almost 2 ppm. But I also noticed bugs swimming around in the skimmer this morning so it’s possible that something other than algae is using up the chlorine right now. I don’t know. I might try vacuuming the piles as opposed to brushing them to see what happens. I just don’t know if I want to vacuum to waste or just filter it. Waste pours out water so fast that I can’t vacuum the whole pool even with a water hose in before getting too low on the skimmer.

 

[aeh0603]

1) If you lost 2 FC overnight, then it's most likely algae. You should follow the SLAM process to get rid of it.

2) It's not dead yet or you would have passed your OCLT. That said, it's safe to swim if FC is between minimum and SLAM level FC per the FC/CYA chart AND you can see the entire bottom of the pool.

3) I'm not convinced it's mustard algae. It looks like dead algae settling to the floor. Either way, you would perform a regular SLAM at the regular SLAM level until you pass all 3 criteria first before raising to mustard FC level. Then you only hold at mustard level for 24 or 48 hours (sorry I forget which without looking it up). Longer then the recommended time at mustard level risks damage to your pool (you could bleach the liner among other things)

4) An automatic floor vacuum is helpful for removing debris, but does not replace brushing. Brushing disturbs the protective biofilm algae creates and allows the chlorine to kill it.

5) No, do not go higher than regular SLAM level for your CYA. Doing so could damage your pool/equipment, will not actually speed up the process, and will mostly be burned off by the sun since it is not adequately protected by CYA.

The best way to speed up a SLAM is to test and dose FC more often to maintain FC at SLAM level. Brush a lot (at least once or twice per day). Remove organic debris from water (vacuum the clumps, remove leaves, etc.)

6) Regular washing should be fine.

7) Vacuuming to filter is fine, in your case there is no need to vacuum to waste.

 

[John2]

1) If you lost 2 FC overnight, then it's most likely algae. You should follow the SLAM process to get rid of it.

2) It's not dead yet or you would have passed your OCLT. That said, it's safe to swim if FC is between minimum and SLAM level FC per the FC/CYA chart AND you can see the entire bottom of the pool.

3) I'm not convinced it's mustard algae. It looks like dead algae settling to the floor. Either way, you would perform a regular SLAM at the regular SLAM level until you pass all 3 criteria first before raising to mustard FC level. Then you only hold at mustard level for 24 or 48 hours (sorry I forget which without looking it up). Longer then the recommended time at mustard level risks damage to your pool (you could bleach the liner among other things)

4) An automatic floor vacuum is helpful for removing debris, but does not replace brushing. Brushing disturbs the protective biofilm algae creates and allows the chlorine to kill it.

5) No, do not go higher than regular SLAM level for your CYA. Doing so could damage your pool/equipment, will not actually speed up the process, and will mostly be burned off by the sun since it is not adequately protected by CYA.

The best way to speed up a SLAM is to test and dose FC more often to maintain FC at SLAM level. Brush a lot (at least once or twice per day). Remove organic debris from water (vacuum the clumps, remove leaves, etc.)

6) Regular washing should be fine.

7) Vacuuming to filter is fine, in your case there is no need to vacuum to waste.

Thank you so much for the thorough reply. I guess I need to reread the SLAM process and the mustard algae process (just in case). I thought I had remembered everything from doing it last year, but I didn’t remember the part about regular SLAM until passing OCLT and then bringing up to higher mustard level. For some reason I was thinking you started off with the highest of you suspected mustard algae. Anyways, now I know, and now I’ll go review the sections on SLAM and in mustard algae to see if there’s anything else I missed.
Two last questions:
1) when dealing with a mostly clear pool with some algae, how many days does it typically take at shock levels before passing the OCLT?
2) I normally run my 2 speed / 2 hp pump on low 24/7. Should I run the pump on high until I pass the OCLT?

 

[aeh0603]

1) No guarantees, but I would expect it to take a few days to a week tops. If it takes longer than that you're either not following the procedure or haven't found where the algae is hiding.

2) Low speed on your pump is fine

 

[John2]

1) No guarantees, but I would expect it to take a few days to a week tops. If it takes longer than that you're either not following the procedure or haven't found where the algae is hiding.

2) Low speed on your pump is fine

Thanks again!

 

[John2]

I hadn’t mentioned this earlier but when swimming under water Saturday I noticed the water wasn’t as clear as it looked from outside the pool, but this is my first full summer with a sand pump so I wasn’t 100% sure how normal that was. I was starting to contemplate adding D.E. to the filter or something to make the water more clear.
But then we went swimming this evening (first time since Saturday) and while swimming under water I noticed the water was already so much clearer than it was Saturday, so that gave me hope that I’m actually making progress!