fighting mustard algae

[Kateyru]

Correction for last addition of bleach, it was 14 ppm. Estimate FC was then 43.5 This morning at 6:30, FC = 36.5. Big drop! Added bleach = +6 ppm so estimate FC = 42.5.

[chem geek]

The last I recall from the other thread is that you have a light in the pool but didn't remove it to get into the light niche. There may very well be a lot of yellow/mustard algae lurking there which means that even if you kill it off in the bulk pool, it will re-introduce itself as soon as the chlorine level drops down below around 15% of the CYA level. It's one of those choices you have to make -- either find and kill the last of the yellow/mustard algae in all dark places it hangs out in the pool or deal with having to inhibit it with one or more of 1) a higher than normal FC that is 15% of the CYA level or 2) use an algicide (such as Polyquat 60 weekly) or phosphate remover at extra cost.

[Kateyru]

Thanks, very helpful. I'm glad to have options tho there is a definite best (get the darn light out). One more question...if we can get the light out after FC is much lower and we can try to remove while we are in the pool, I'm guessing that I would have to do the mustard algae shock treatment all over again, correct?

Also, based on additional reading, I think the stuff I see around the bottom edges of the pool is probably stains rather than mustard algae.

Many thanks again!

[BigDave]

You probably can get in the pool (CYA 50+ppm FC 30+ppm). Wear an old suit(you don't care about), cover your hair, work quick, take a shower. maybe better than letting it drop, doing the work and then starting again. Your choice.

[Kateyru]

I didn't remember correctly about the light. My husband got in the pool before I started shocking. The screw was so rusted that he was afraid it would break off and cause more serious problems. any suggestions about that?
I'd also thought I get our pool guy to try to remove the light as he likely has more experience....tho a service call is $75.
Thanks!

[Kateyru]

Update: Pool guy wasn't willing to try to remove pool light. Hope no lurking algae back there but time will tell. I removed the treads on ladder the other day while still shocking.

I'm now letting FC drift down. Water looks great, very clear. FC = 7.5 this morning. On Thursday, CYA wasn't showing up when tested (not sure what happened) so I added 3 lbs. through a sock. That being 1/2 the amount needed to get CYA to 70. I am leaving town in the morning for 2 weeks. So, I won't get an accurate read on CYA until next Thursday???? What do you suggest about adding more CYA? I'm checking FC and pH daily.
Thanks.

[aylad]

If you're planning to run your SWCG, you need to add whatever amount of CYA the manual for your unit calls for, and that' usually around 80 ppm. If you are not running your SWCG, do you have somebody to take care of the pool while you're gone for 2 weeks, so you don't have to start over when you get back?