Recurring Mustard Algae, Have a Pool Party this weekend

Algae problems in swimming pool water.
Green (cloudy) water or slimy pool walls.
Black algae. Mustard algae. Pink or white pool mold.
electrocat
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Joined: Mon 20 Nov, 2023 20:51
My Pool: Salt water, roughly 50000L (about 9mx5m)
I'm unsure about surface, possibly fiberglass? (Definitely not tiled)

Recurring Mustard Algae, Have a Pool Party this weekend

Postby electrocat » Mon 20 Nov, 2023 21:22

Problem: Renting a house and when we first moved in (Dec last year), something was wrong. First time pool 'owners' also. After some research, realised it was mustard algae, used local pool store to advise how to get rid of it and were able to. It was pretty bad. Pool was fine until about September, when for personal reasons just couldn't keep up with it, and the mustard algae came back. This time I did some research and fixed myself by shocking the pool, threw out any old pool toys and put the equipment in the shallow end to be shocked also. I then organised for a monthly pool service to be done, the last one was done on the 9th of November. Yesterday evening my daughter alerted me that the pool looked 'green' and when I checked, it was free of debris and the vacuum was running - but mustard algae was present. Although it's spring here (Australia) the weather has been ordinary and so we haven't been in the pool. But the outbreak was fairly significant, not as bad as before but had definitely been present for a week or so I would think. The problem is, my daughter is having her birthday party - a pool party of course - this Sunday. It was too late in the day for me to call the pool shop, so I started actioning it asap.

I:
- vacuumed the pool to waste to try to clear what I could first
- checked pump and skimmer baskets were clear
- brushed the walls, steps etc
- tested water (can't remember results exactly, but all were in normal range including FC. FC & CYA are the only ones I can remember - 3ppm & 40 respectively, pH was also 7.2)
- shocked using hyclor super shock (cal hypo) and after researching, used a higher amount to try to hit 16ppm FC. This took some working out, and I've just realised I did the maths wrong. The product is 700g/kg chlorine. I used 1480g (based on daily dose of 40g per 10,000L, super shock recommendation on the box to get to 10ppm FC is 4 x daily dose. So I did (((40g x 5) x 4) / 10) x 16 but I did 1480g instead of 1280g. Which is 18ppm target I guess. I hope this isn't too bad. I added the shock at night, about 930pm, turned filter on.
- tested 10am this morning (these are the results below) - but my test strips I have realised are not that sensitive!
- Pool looks 'blue' now, not green at all, but cloudy. There were some algae particles present on the steps and edges - but significantly reduced.

Now, should I leave the shock work longer? How long? How do I know if I over chlorinated and that's why it's cloudy? Or if it's just dead algae?
When should I backwash the filter?
I have HyClor Cloudout and HyClor Multi-cube tablets. Both of these seem to do the same thing to me, but which is better to use and when should I use it? Should I vacuum both before and after the clarifier, or just after?
Today is Tuesday, so I have a few days up my sleeve before the party.

FC: 10+ (my test maxes out at 10 and I haven't got an alternative yet!)
TC: 10+
pH: 7.2
TA: 80
CH: 250
CYA: 40
(my test strips are not very specific and I am aware I need to source better ones)

My pool: All I know is it is a salt water chlorinator, sand filter, roughly 50000L, I think the surface is fibreglass (definitely not tiled). I can try and answer any other questions if you have them.
Pool chemicals: Not 100% sure what the pool company uses. I've used HyClor Super Shock only so far. I have stabiliser, dry acid, soda ash, long life algaecide at my disposal if needed too.


Teapot1
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Joined: Thu 29 Apr, 2021 00:43
My Pool: 12000 gallons vinyl liner,

Re: Recurring Mustard Algae, Have a Pool Party this weekend

Postby Teapot1 » Tue 21 Nov, 2023 03:05

Cloudyness is dead algae. Dont panic, whilst clarifyers work it takes a lot to clear and time is not in a bottle from the pool store.

You could use a flocculent, put the filter on recirculation and add flocculent via the skimmer but not too fast. Let it mix and then switch off, the dead algae will clump together and sink to the bottom over about a day. You can then vacuum the debris out on the waste setting but put the top up hose in or you'll quickly drop the pool level, good luck and fingers crossed.
I may not give you the answer you want to hear, but I will give an honest opinion of your situation as you decribe it.
Pranav
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Joined: Sun 26 Nov, 2023 05:08

Re: Recurring Mustard Algae, Have a Pool Party this weekend

Postby Pranav » Tue 28 Nov, 2023 01:39

Teapot1 wrote:Cloudyness is dead algae. Dont panic, whilst clarifyers work it takes a lot to clear and time is not in a bottle from the pool store.

You could use a flocculent, put the filter on recirculation and add flocculent via the skimmer but not too fast. Let it mix and then switch off, the dead algae will clump together and sink to the bottom over about a day. You can then vacuum the debris out on the waste setting but put the top up hose in or you'll quickly drop the pool level, good luck and fingers crossed.

Excellent advice! A sensible technique to deal with pool water concerns is to use a flocculent on recirculation mode, then allow the clumped algae to settle before vacuuming on the waste setting. Being mindful of the water level throughout the operation promotes a thorough clean with minimal water loss. Good luck with the pool upkeep!

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