Am I battling mustard algae ???

lsegeorge · Dec 19, 2016

My greetings to the Group

I have a plaster/pebble pool (Beadcreete) which I have been treating for an algae infection for the past two weeks. This involves slam level chlorine and brushing with a stainless steel brush, daily at the beginning, less often now. The pump was on continuously for the first week and 6 hours a day for the second

I was able to get rid of most of the visible algae but the following still troubles me.

The floor of my pool, has a kind of beige/ yellowish colour at certain areas. Even when the steel brush stirs up the dead algae powder (or the vacuum sucks the powder) this beige colour is still there.
I am a bit confused in that I am not entirely sure whether this hue was there in the first place, whether it’s some type of persistent algae, or whether its discolouration of my plaster?
I have taken a few pics (attached) of a certain spot of my pool where the bottom plaster has this yellowish hue with two circles being noticeably bluer. To me this seems like evidence that my pool was not always like this. I am wondering if this is evidence that I am battling mustard algae?

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domct203 · Dec 19, 2016

lsegeorge said:
My greetings to the Group

I have a plaster/pebble pool (Beadcreete) which I have been treating for an algae infection for the past two weeks. This involves slam level chlorine and brushing with a stainless steel brush, daily at the beginning, less often now. The pump was on continuously for the first week and 6 hours a day for the second.
I was able to get rid of most of the visible algae but the following still troubles me.
The floor of my pool, has a kind of beige/ yellowish colour at certain areas. Even when the steel brush stirs up the dead algae powder (or the vacuum sucks the powder) this beige colour is still there.
I am a bit confused in that I am not entirely sure whether this hue was there in the first place, whether it’s some type of persistent algae, or whether its discolouration of my plaster?
I have taken a few pics (attached) of a certain spot of my pool where the bottom plaster has this yellowish hue with two circles being noticeably bluer. To me this seems like evidence that my pool was not always like this. I am wondering if this is evidence that I am battling mustard algae?

View attachment 56053View attachment 56054

While mustard algae could be a possibility, it is somewhat unlikely from what you describe. Mustard algae tends to grow in clumps, and in the shade.

Pool School - Mustard Algae

You've mentioned that you SLAMmed the pool, but the sentence I highlighted in your quoted post is worrisome... A SLAM is not complete if you still have any visible algae. Also, it is recommended that your pump & filter run continuous during a SLAM, not just during a part of it.

To truly understand your situation we know if you really did complete a SLAM or not. Did you meet all the criteria needed to complete a SLAM?

Pool School - SLAM

This would mean:
1) Pass OCLT (Pool School - OCLT)
2) CC is >0.5ppm
3) The water is clear, including visible algae.

If you had indeed met all three criteria and then noticed that yellow substance then mustard algae could be an issue. This could just be discoloration from algae that has not been completely eliminated.

Can you please post a complete set of test results including:
FC
CC
pH
TA
CH
CYA

JamesW · Dec 19, 2016

Might be iron stains. Try a little bit of vitamin c (ascorbic acid) on a spot. If it clears right away, it's probably iron.

lsegeorge · Dec 19, 2016

I just took measurements but I need to explain what I am doing first.

1)My swimming pool was going through some pretty bad algae infection.
2) I was due to change my water to lower my CYA.
3) I had a bucket full of Trichlor tablets which I stopped using since moving to liquid chlorine

So what I did, I started using large amounts of trichlor to shock my pool.
The plan is to do the water change when I finish with the treatment and to go back to liquid chlorine to maintain CYA.

So the measurements are:
- CYA: 260 (I diluted the water 3 parts tab water to 1 pool water) and got a measurement of 65)
- FC: 55ppm (at 110 drop the water turned from pink to grey)
- CC: 0 (the water did not get pink, although measurement may have been affected from previous step)
- Ph: 7.6 (not sure it matters at this sort of FC levels)

domct203 · Dec 19, 2016

lsegeorge said:
I just took measurements but I need to explain what I am doing first.

1)My swimming pool was going through some pretty bad algae infection.
2) I was due to change my water to lower my CYA.
3) I had a bucket full of Trichlor tablets which I stopped using since moving to liquid chlorine

So what I did, I started using large amounts of trichlor to shock my pool.
The plan is to do the water change when I finish with the treatment and to go back to liquid chlorine to maintain CYA.

So the measurements are:
- CYA: 260 (I diluted the water 3 parts tab water to 1 pool water) and got a measurement of 65)
- FC: 55ppm (at 110 drop the water turned from pink to grey)
- CC: 0 (the water did not get pink, although measurement may have been affected from previous step)
- Ph: 7.6 (not sure it matters at this sort of FC levels)

With a CYA of 260 ppm, you would need to reach and maintain a FC level of 104ppm (40% of CYA) for the duration of the SLAM to effectively oxidize the algae faster than it can reproduce.

You should address the extremely high CYA level before you go any further.

You could also try the Vitamin C test that JamesW suggested, but you still need to address that CYA.

Where are your TA and CH levels?

lsegeorge · Dec 20, 2016

Thanks for the feedback.
A couple of questions if I may!

Say I want to reduce CYA to 50. Should I leave 15% of my old water and replace 85%??

15% * CYA360 = CYA54 (assuming that CYA in the new water will be nil)

So for my 50m3 pool I should replace 43m3 and keep 7m3??

kimkats · Dec 20, 2016

We almost never say to drain a pool 100% just to be on the safe side. Don't want any problems to happen-pool heave, liner floating, side collapse, etc. You seem to have done the math so I say go for it. Just use care you do not drain ALL of the water :shock:

we don't want any liner problems.

Kim :kim:

domct203 · Dec 20, 2016

lsegeorge said:
Thanks for the feedback.
A couple of questions if I may!

Say I want to reduce CYA to 50. Should I leave 15% of my old water and replace 85%??

15% * CYA360 = CYA54 (assuming that CYA in the new water will be nil)

So for my 50m3 pool I should replace 43m3 and keep 7m3??

Your math is correct.

As Kim has mentioned, we are reluctant to recommend completely draining a pool. The ground water level can float a liner, or even float an entire pool shell up and out of the ground.

https://www.google.com/search?q=POO...nYPRAhXHRiYKHf6jCL4Q_AUICigD&biw=1406&bih=837

Do you know the underground water level (water table) in your area? Draining below that level can lift a concrete shell out of the ground.

Also, I notice quite a difference in your CYA level in today's post. Yesterday you posted a CYA of 260ppm (diluted 3:1 of 65). Today you post it as 360ppm.

Are you checking your CYA outdoors on a bright sunny day with your back to the sun, holding the comparator block at waist level, in the shade of your body? Indoor lighting will not give accurate results.