does anyone know what this stuff is and how to remove it

[rjack1282]

Newcomer to the forum here.

Does anyone have a clue what this substance is on my pools walls? It's green, hard, and gritty and seems to be imbedded into the plaster. I have tried scrubbing it off with a steel brush to no avail. Since the attached picture was taken, I have added water (low level in picture), shocked, brushed, vacuumed, cleaned filter until the water is clear with no new algae forming. This stuff refuses to come off no matter how much I scrub.

 

[bobodaclown]

Rub a trichor puck against it. If it lightens you might be able to use that to get rid of it. If not then try a vitamin C tablet against it. If it lighten then its metal staining.

What's the surface of the pool?

Others will chime in with time.

I hope its not black algae. It takes longer to go away.

Also Mr. Clean Magic Eraser may work on the tile or an acid wash if its calcium staining.

 

[duraleigh]

Well, I have to guess on this one so take it for what it's worth......

Your description and it's appearance make me think it is a combination of calcium scale and algae. The calcium scale comes from pH too high over a pretty long period and, algae can accumulate and grow in it. The result is VERY hard to kill algae because it can "hide" in the scale and, like you said the scale alone is quite difficult to remove.

I think you are going to have to lower the water line and treat the scale directly with a good dose of muriatic acid and then shock your pool to get rid of the conditions that have encouraged the algae to grow.

 

[carolina pool]

In the picture it looks brown above the waterline which would indicate iron, dead algea or tannic acid stains. The tile also appears to have a good bit of scale. If you have a heater it could be copper. I think duraleigh got it right.

 

[y_not]

BTW, this is what we mean by "shocking" your pool.
pool-school/defeating_algae

It's a process, not a product you dump in and call it "shocked".
Read the 1st link at the end of the article as well. You will need a FAS-DPD chlorine drop test kit to perform this procedure, they are discussed here.
pool-school/pool_test_kit_comparison

 

[rjack1282]

Thanks for the info so far.

Here are the numbers...

FC = 38
CC = 0
TA = 90
CH = 370
CYA= 60
pH = 7.5

I have been holding the FC above shock level for my CYA and it's not going away. It must be a dead algae/calcium scale mixture as duraleigh suggested. I will probably have to drain and treat directly.

 

[y_not]

Are you brushing it regularly while at shock level?

As for draining, an alternative would be to keep your water on the negative end of the ceiling index. With regular brushing it'll go away.