Pool is clear but bottom looks spotty and dirty

[BigDave]

If you do decide to add more CYA, remember to raise the FC targets as well (for shock and regular maintenance).

[rkrgk]

I decided to wait before adding CYA since I am backwashing the filter almost every day. I put the CYA (granular) directly in skimmer and I am afraid it will all be gone when I backwash. Pool is still not looking completely clean. Its hard to remove them. And they dont seem to be turning brown at all, the algae that I catch are all the ones that I brush off from the walls and get caught in fine mesh skimmer and the filter. I was hoping that once I brush the walls a bit, algae should come off quickly and turn brown. I maintain the shock level of 15ppm all the time. The walls are a bit blackish, but the algae that get caught in the skimmer mesh is green.

[BigDave]

I don't remember if you're using the pool yet or not. Perhaps you need to move to the +shock+ column of the chart. I recall reading that black algae can be very hard to kill and digs in to the pores in the surface and hangs on tight.

A couple other thoughts:
Is it still pollen season in your area? - might explain the green stuff in skimmer.
If the pollen is over and it's green(live) algae (wich clogs filters quickly), I'd guess that there's more CYA than measured or FC is dropping too low (Phoenix sun). Either way, my suggestion would be to raise the FC level to +shock+.

[rkrgk]

Yeah, I was just about to ask you if I should use a higher level for FC. No, they are algae (I think we have less pollen currently). Every time I brush they come out of the walls a bit by bit and get caught in the secondary skimmer after few hours(fine mesh) and the pressure of the filter rises +5 within next day or so. I backwashed the filter 4 times this week itself. The algae on the walls are not turning brown at all. They are still black and looks dark green when caught in skimmer mesh. To make matters worse I have a popup cleaning system (caretaker) which doesnt work well under high filter pressure. I have to maintain the sweet spot of 28-30psi or else they dont rotate, I think there is something I am unable to understand what to do.
I swim during the weekend, looks like good weather for this weekend, may be we will use it this weekend and start on the +shock+ levels. I will check CYA again tonight if its wrong. Thanks BigDave.

[BigDave]

Wear an old swimsuit and have fun!
It's going to be a while for us - the pool made it up to 60 yesterday.

[rkrgk]

Here it is 101 today!

I have been continuously putting bleach and brushing the pool everyday for the past two weeks, maintaining atleast 15ppm of FC, I am starting to up the chlorine to 30 since I think its not that easy to get rid of them. The black spots are almost like plaster. Is there any thing else I can do to make it easier to shake them out and remove them? I am able to get rid of them, but only little by little and not sure if I can remove them completely. Its harder to remove them in the deeper part and under the water fall where it is hard to reach. Can I somehow brush them off with some concentrated chlorine or something?

[rkrgk]

I read in some other posts about using polyquat. Is that effective to remove black algae easily from the walls? Seems like I may be just losing the battle against the algae although I made huge progress, still algae is not completely removed even though I brushed the same place a 100 times, they are so stubborn. Unfortunately I was sick for few days and still recovering.. so physically I may not be able to do much brushing for couple of days as well.

[BigDave]

Polyquat (the only algecide recommended here) is better at preventing algae than killing it. It also creates a chlorine demand when added to the pool. The best advice I can give is to maintain the +shock+ FC levels. Perhaps somone else will chime in with another idea.

I glad to hear you're making progress - don't give up.
I hope you feel better soon.

[robbym70]

I am really interested to know how people remove algae without a wire brush.....

My set up is totally different than yours but when I need to scrub the walls of my vinyl pool I use a stiff nylon brush. I thought maybe switching to a stiff nylon brush might be a good alternative for you if you think the wire brush is damaging the surface of your IG pool. Couldn't hurt trying it out.

[rkrgk]

My set up is totally different than yours but when I need to scrub the walls of my vinyl pool I use a stiff nylon brush. I thought maybe switching to a stiff nylon brush might be a good alternative for you if you think the wire brush is damaging the surface of your IG pool. Couldn't hurt trying it out.

I am having a tough time removing the black algae spots even with the wire brush. I think black algae may not stick to vinyl surface as it would to a gunite surface? I have scrubbed the walls everyday for three weeks continuously while maintaining a +shock+ level of FC, I got so tired, but still there are algae spots. I think there is has to be an easy way to remove them without draining and acid wash, but I just dont know what that is. Its almost gone, and is much better now, but I would like to remove the remaining patches somehow which does not come off even with a wirbrush. I was going to try some strong algecide as my next plan.