Small Black Round Things

[WetBehindTheEars]

My pool has always had these 5mm in diameter round black slightly convex deposits stuck to the plaster. I can scrape them off with my fingernail but they are not affected by brushing. They scape up as one piece...I hate to say like a scab (guess I just did). The pool is next to a rather large oak tree that does have lots of debris. Any ideas what the deposits are? They are getting much more numerous and I don't know what to do.

Thanks.

 

[Suziqzer]

Pictures always help ....

 

[Butterfly]

Round, black, getting much more numerous.......Black algae?

Are you brushing with a wire brush?

Have you tried rubbing with a trichlor tab?

If it is BA, you need to shock and brush and brush to keep the tops knocked off so the chlorine can kill it.

 

[duraleigh]

Agreeing with Butterfly's analysis, I suspect black algae as well.

Sounds like you need to shock the pool. Pool School will tell you the procedure that needs to be followed.

 

[cya_sux]

Could it be some sort of tree sap?

If you think it might be black algae, move that return so its pointing towards those black things and see if they go away. I don't think its black algae though.

 

[WetBehindTheEars]

I'm testing pool later this morning but I've had these since buying the pool and I've only had a CC reading higher than .5 once...and that was in November when the oak tree was hating me.

The concentrations tend to be on the opposite side of the return nozzles. I have not used a wire brush...is that ok on plaster?

I don't think I own any trichlor tabs...previous owner I believe just shocked the pool once a week. His dogs swam in pool so I always thought it was related.

Now that it is getting a bit worse I guess I have to consider algae or something seasonal from the tree.

 

[Bama Rambler]

So you're saying that when you scrap them off the whole thing comes off clean (or almost)?

If it's black algae when you crush them, the inside is green and slimy, just like regular green algae.

 

[Butterfly]

I have not used a wire brush...is that ok on plaster?

Use a wire brush or a combo brush or you can get a smaller wire algae brush.

Nylon ain't gonna do nothing for BA in a plaster pool but make it mad.

ETA: Even if it turns out not to be BA, you need a wire or wire combo brush for your plaster pool.

 

[Butterfly]

Found better info for recommending brushes:

Nylon is for vinyl, fiberglass, tile, and plaster that is less than one year. (Plaster includes any exposed aggregate and marcite finish, btw!) Combo brushes are for older plaster. All stainless are for algae (very stubborn green algae and also the ONLY brush for black algae.)

You CAN unscrew the Wall Whale from the nylon brush it comes with and screw it on a combo brush if your plaster is over a year old. Newer plaster is really too soft for anyting other than a nylon brush.

 

[WetBehindTheEars]

This is a poor pic of the stuff on my fingers. It is very flat and does not seem to have a green type center. I'll test pool once the kids let me and I'll pick up a wire brush today. The stuff seems to like crevices of course. If it were algae wouldn't I have had CC readings higher than .05? Thanks for help.

 

[WetBehindTheEars]

Just checked pool CC is .5. Can I have algae and an acceptable CC level?

I need to add bleach and muratic acid per calculator.

 

[duraleigh]

Can I have algae and an acceptable CC level?

Yes.

 

[chem geek]

This is a poor pic of the stuff on my fingers. It is very flat and does not seem to have a green type center.

Rub/squish it on a white piece of thick paper. If it stains it green (even dark green), then it's algae.

 

[taekwondodo]

+1: Looks like BA to me...

 

[frankgh]

I had a large out break of Black Algae myself. I scrubbed each head off individually with a pumic stone, brought the CL up to 20 and brushed with a stainless steel brush everyday for about 5 days. Black algae is now gone!

 

[WetBehindTheEars]

Ok. I tried the paper test and my wife (used to be a printer) did not think it looked green. But see picture...where I brushed with metal brush yesterday looks much better. I can't risk full blown BA so I will treat this as such regardless. After the boys swim this evening I will ramp up the bleach and go for a good burn. Any suggestions beyond FC of 15 to 24 sustained for the week with regular metal brush scrubbing?

Yesterdays readings before adding bleach and 32oz of muratic acid.
FC 1.0 / 5 goal
CC .5
pH 7.8 /7.4 goal
TA 80 / 79 goal
CH 470 / 350 goal (slowly coming down)
CYA 40 / 40 goal
CSI .34
TEMP 78

 

[Butterfly]

Shock level........ What is your CYA level?

 

[WetBehindTheEars]

Butterfly...40 CYA...I was editing while you were typing.

 

[Butterfly]

Butterfly...40 CYA...I was editing while you were typing.

Okay, your plan sounds good.