Still struggling with Black algae, Chlorine Dioxide?

[Bperry]

The pictures look more like worn away plaster than black algae to me. My pool is the same size and same age and has plaster chunks missing like that. Are you sure it’s not just the dark gunite showing through chipped plaster?

 

[Mdragger88]

Yes, when I was keeping my FC high after treating for Yellow Algae. I didn't note all my FC levels on my pool math page. I wasn't sure how to use the pool math page during treatment cause all I was testing was chlorine at that time. I did keep written notes and see that from Aug 1st to Aug 20th my FC level ranged from 26 FC to 22 FC. This was 19 days of high FC plus I did two phosphate treatments during this time. As well I was wirebrushing the black algae spots and breakouts and rubbing trichlor pucks over the areas a couple times a day.. very little noticeable change in the BA.

For future reference you can always just log one parameter/addition (like fc) & save your log. It will just use the last record for the other parameters on the main page. It Doesn’t mess anything up & allows u to keep good records. I hope the bleach sprayer option gains u some headway on your issue.

 

[aqua mango]

The pictures look more like worn away plaster than black algae to me. My pool is the same size and same age and has plaster chunks missing like that. Are you sure it’s not just the dark gunite showing through chipped plaster?

Interesting thought. I have other spots on my pool floor with worn out patches that don't show this black stuff underneath though. Also I have noticed at times it will flare up and look blacker as well as new black spots appearing on my stairs and walls. I will follow the bleach sprayer idea and see how the black spots respond.

 

[aqua mango]

For future reference you can always just log one parameter/addition (like fc) & save your log. It will just use the last record for the other parameters on the main page. It Doesn’t mess anything up & allows u to keep good records. I hope the bleach sprayer option gains u some headway on your issue.

Thank you

 

[Bperry]

Interesting thought. I have other spots on my pool floor with worn out patches that don't show this black stuff underneath though. Also I have noticed at times it will flare up and look blacker as well as new black spots appearing on my stairs and walls. I will follow the bleach sprayer idea and see how the black spots respond.

If they flare up then, yea may be algae. I had some a month or two ago and I poured liquid chlorine from the bottle down onto them during a SLAM and that took care of them. You probably just need a lot more chlorine.

 

[cowboycasey]

I have never found the trichlor pucks to work for me. Find whatever method works to disrupt the bio film. Wire brush, wooden pick, even a pressure washer. Then hit it with as much concentrated LC as you can. The pump sprayer works best I have found (method pioneered by @cowboycasey).

Please just do me the favor of trying this out. Then we can discuss all the rest of your ideas.

It does work great and just by chance I thought of it one day... some 10% or 12.5% in a sprayer should get after it great..

 

[aqua mango]

You absolutely DO NOT want to mess with chlorine dioxide. It is seriously dangerous stuff when it is not properly handled and dosed and you could easily hurt yourself and others you love. There is reason why chlorine dioxide is not used in swimming pools and it's because of the safety hazards it poses. Yes, it can be used in large commercial pools and water treatment facilities where there are control systems in place for proper handling, injection and monitoring, but that is not your backyard pool.

Chlorine dioxide is a gas, not a solid. The solid stuff is sodium chlorite which you are expected to mix with an acid in order to generate chlorine dioxide gas. This is a very difficult thing to do in a pool and, as I said above, can lead to potential poisoning. People have died messing around with stuff (aka, "Magic Mineral Solution").

If your pool is going to be replastered then you just have to live with the black algae until it is. Do a full chip out of the paster and have the contractor chemically sanitize the concrete shell by doing an acid wash and a bleach wash. High pressure steam can also be used to sanitize concrete surfaces that have algae problems. Then the contractor can apply a new plaster layer.

Just rereading your good advice.. we are not at the time to replaster our pool so I will follow your good advice. Thank you for all the details most appreciative.