Recurring algae on walls

buzzard302 · May 13, 2014

This forum has been a wealth of information to me, thank you. I bought a home 1 year ago with a 10k gallon in ground pool. Pool was resurfaced by previous owner about 5 years ago with Daimondbrite.

I have been maintaining the pool (with bleach) on my own, almost over obsessively. I use a Taylor K2006 test kit. The pool is open, full sunlight all day in south Florida. Test results are:

FC: 7
CC: 0
CYA: 40
TA: 70
CH: 230
PH: 7.4
Borates @ 50ppm

I never let FC drop below 5 and pass OCLT regularly. I brush every Sunday. Yet by the following Saturday, I continue to get a light bit of algae on the wall of my pool, particularly in the shallow end near the steps. The water is literally crystal clear, and I maintain water chemistry daily. So can anyone offer an explanation as why this keeps happening?

Casey · May 13, 2014

Welcome to TFP. Is the Mustard on a shaded wall? If so, you may have to do a Mustard Algae SLAM until it clears and run a higher FC. I'd also brush your pool 2 times a week instead of 1x.

JohnT · May 13, 2014

Welcome to TFP!

What color is the stuff you find on the wall?

buzzard302 · May 13, 2014

Casey said:
Welcome to TFP. Is the Mustard on a shaded wall? If so, you may have to do a Mustard Algae SLAM until it clears and run a higher FC. I'd also brush your pool 2 times a week instead of 1x.

Hi Casey, the algae is on a wall that would be shaded early in the morning, but receives full sun the rest of the day. I have slammed twice over the past year, and the algae will recur usually within 3-4 weeks of slamming.

JohnT said:
Welcome to TFP!

What color is the stuff you find on the wall?

I would say it is yellow/green in color.

Richard320 · May 13, 2014

It sounds like poor circulation to me. Try re-aiming a return jet to cover the step area better. And brush the algae area more than once a week. A wall whale brush will move a lot of water. I mean, enough to bend the pole if you have it set to maximum thrust.

duraleigh · May 13, 2014

I would say it is yellow/green in color.

The color, combined with it's appearance on the walls indicates mustard algae. Does it "poof" into a yellowish-greenish cloud when you brush it? That also indicates mustard algae.

I also have it in my pool in the same spots every year. Adequate chlorine (SLAM value for mustard) will remove it and keep it away but you have to monitor it carefully.

buzzard302 · May 13, 2014

Richard320 said:
It sounds like poor circulation to me. Try re-aiming a return jet to cover the step area better. And brush the algae area more than once a week. A wall whale brush will move a lot of water. I mean, enough to bend the pole if you have it set to maximum thrust.

This has crossed my mind, but the circulation is very good in the pool, and the pump runs about 9 hours a day. There are two return jets at the opposite ends of the pool, and they create a nice circular flow through the pool. I'll double check the aim.

duraleigh said:
The color, combined with it's appearance on the walls indicates mustard algae. Does it "poof" into a yellowish-greenish cloud when you brush it? That also indicates mustard algae.

I also have it in my pool in the same spots every year. Adequate chlorine (SLAM value for mustard) will remove it and keep it away but you have to monitor it carefully.

Yes, agreed it is Mustard algae. It definitely "poofs" when brushed. I may try a Mustard algae slam for an extended period.

I don't think it helps that the pool is unscreened and susceptible to quite a bit of organics, including lawn clippings and constantly falling leaves.