Trichlor Pucks on black algae procedure

drewh

Well-known member
Oct 19, 2014
101
Brisbane, QLD, Australia
#1
Hi all,

Before I SLAM to get rid of the other algae that's plaqued my pool, I want to properly remove the two actual spots of black spot algae. Just wanted to check I'm following the 100% right procedure.

I started yesterday - at first brushed them vigorously which actually made the spot larger (as if some algae was coming out from under the protective membrane) but it also showed where the membrane is. Then I placed a trichlor puck on part of one spot, left it about an hour, took it off and scrubbed it etc. have repeated that today again for a 2 hour period. But I'm noticing it's not really getting less, or if at all only a very very small amount. I suppose the algae has been there for some time so might even take multiple pucks to remove? Most articles mention 15-20 mins but for these that is nowhere near enough, it's looking like I'll need them on each for whole days at a time. I don't have a tool to rub them on it but tried to a bit with the pool pole.

So checking the procedure is ok to just let them set on each algae, then every 2 hours move it and brush more with ssteel brush, then move the pucks back on? Do I need to press down on them with the pole? My CYA is 25 so it wouldn't matter if the few tablets end up adding some to it.

See pics below (first pic is one spot as it's been for months, then after brushing very rigorously has spread more, same with the other side in next two pics).

Appreciate everyone's help here!

Pics - one spot leaving it as is for months:



After vigorously brushing yesterday & up closer, but it's spread in size


Second spot before brushing


second spot after brushing
 

jblizzle

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May 19, 2010
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Tucson, AZ
#2
Have you scrapped some off with your finger nail and spread it on some paper to confirm that it is indeed algae? (It will show as green on the paper).

Hoping that you are not brushing away your plaster and exposing the shell.
 

drewh

Well-known member
Oct 19, 2014
101
Brisbane, QLD, Australia
#3
I haven't because both are in tricky places in the deep end, not easy to reach short of diving down and then I don't have goggles atm.

Now you've got me worried... the two marks have been there for a while and both started as round & firm like black spot algae.

Isn't that second shot exactly how it is re the protective shell/membrane? So I must be brushing some of the algae out from underneath it..?
 

jblizzle

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TFP Expert
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May 19, 2010
41,197
Tucson, AZ
#4
I have no idea, never seen black algae, but why would the membrane be the same color as the plaster?

To me it kind of looks like maybe acid was pooled on the bottom on a low spot and etched away the plaster ... but I could certainly be wrong.

Seems like you should really get down there and feel it and try to get a sample.
 

drewh

Well-known member
Oct 19, 2014
101
Brisbane, QLD, Australia
#5
I thought you'd seen everything known to man re pools jblizzle ;)

Look how clean the circular edge is to the membrane. I've brushed vigorously over that whole area in the last pic. If it was the plaster why would there suddenly be that section not coming off? It would have all come off fairly uniformly (given the scrubbing).

I will try to get a sample tomorrow. Remember my pool has that black algae that appears all over also (re other thread) but that brushes away completely. These two spots are very firmly in place and don't brush away (which I thought was consistent with actual black spot algae).

Will let you know what I find tomorrow (past midnight here in Aus).... hoping it's not the plaster being brushed away, have me worried now.
 

drewh

Well-known member
Oct 19, 2014
101
Brisbane, QLD, Australia
#6
jblizzle you were right :( :( :( :( :(

Oh man, I can't believe I didn't realize that myself. Both started as little circles & I assumed it was black spot algae. But I can see now looking closely from in the water it was a weak area of marblesheen and I've just made the area larger by brushing so hard. Man..... I want to cut my arm off right about now. How could I have let that happen?!

Is there a product I could use to patch those spots up? I can actually see looking really close from under water areas around it where it's also weaker and will prob start to break off (like you imagine paint that has rust underneath and the paint looks thin).

Gee that sucks, if I'd left it alone it didn't look that bad, esp the right side mark. Am shattered!
 

jblizzle

Mod Squad
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May 19, 2010
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Tucson, AZ
#7
That sucks. Sorry we were not able to figure it out sooner.

I am not sure there is an easy fix.
How old is the plaster?
 

drewh

Well-known member
Oct 19, 2014
101
Brisbane, QLD, Australia
#8
Not your fault, I prob should have got in and checked it up close sooner, just assumed it was black spot because of how it started re round. Still wonder why that other one has the circle around it almost like a membrane. I'm just glad you suggested that as otherwise I might have done more damage, so I owe you one.

I googled and some people have said they just paint over the exposed part. That would mean draining the water etc., might only be worth doing that next year in the off season months.

Plaster (it's actually marblesheen which is white cement with marble chips in it) is 20 years old. It has aged quite well though, still looks good for the most part).
 

jblizzle

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May 19, 2010
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Tucson, AZ
#9
Paint is very temporary. Only send to last a year or two and starts to flake or fade so you have to do it again. Plus sounds like you have more marble that is ready to flake off. After 20 years, I would suggest saving up and getting the pool resurfaced is the correct repair option.
 

drewh

Well-known member
Oct 19, 2014
101
Brisbane, QLD, Australia
#10
Yes you're right though I'm not sure if I'll be in this house more than 1-2 years (it'd be rented after that) so given that wouldn't make sense to spend on that now.

Here in Aus Selleys have a Quikcrete product that specially has one use case of pools. This actually rebuilds the marblesheen layer and then that is painted. Because it's white cement that makes up a lot of the marblesheen, it might not matter if the paint flakes or fades of the Quikcrete is white underneath?

Will probably end up leaving it for now. I'll get used to it and all things considered it could have been worse. I won't make the same mistake again!
 

duraleigh

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Apr 1, 2007
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Sebring, Florida
#11
Sorry about your plaster. Your thread brings up two points....unrelated.

1. ANY stain must be properly and positively identified before you try to fix it. That seems so obvious but the path of least resistance for all of us is to take a guess at the stain and then throw something at it. More often than not, it fails.

2. Keep your subjects under one thread whenever possible. More than once you reference somewhat pertinent material in another thread. Most of us will not go to that other thread to see what you are talking about......we simply move on to another's thread.

Your pool's "story" is most always interrelated and we can see and understand that story much better when you stay within one thread.
 

drewh

Well-known member
Oct 19, 2014
101
Brisbane, QLD, Australia
#12
Yes you're right, my reasoning was the colour, initial shape (round) and that both appeared to have a membrane versus just a solid block. I won't make the same mistake again re any algae or any diagnosis.

Re 2, the reason I started a new thread was the main one had some 30+ replies so was very long, and that this stuff I believed was black algae was different to the other algae (also black in colour) that's strewn around the pool & the other thread discusses. So I didn't want to confuse people. When keeping it in one thread, should I repost pics if I'm referring to them in a post vs saying 'pics are at start of thread' etc. Want to make it as easy as poss for people, and as always greatly appreciate all the excellent help - such a great community TFP is.
 

duraleigh

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#13
Keep the pics and descriptions in one thread. Frequent responders, like myself, find it very difficult to switch between active threads started by the same member. It is very easy for us to stay in one thread and scroll up to find any other pertinent info.


It may seem counter intuitive to some but starting new threads reduces your exposure as many people will simply pass the new one by thinking they have already seen it or answered it.
 

swoopman

Well-known member
Jul 26, 2014
213
Annapolis, MD
#14
I am sorry to hear about your plaster. I had some areas in the pool where I believe the plaster was damaged due to poor pool chemistry (before me caring for it using TFP).

I used EZ Patch to fix. They make a fast set that can be used underwater. I have white plaster so used the white but I checked and they make it for various finishes too. I don't know if it's available to you there or if one of the available finishes will work for you.

Just did this at the end of this past season. It was easy to use and looks good but I am not able to say how well it holds up over time.

http://www.e-zpatch.com/Products1.html

Maybe that will be of some help.
 

drewh

Well-known member
Oct 19, 2014
101
Brisbane, QLD, Australia
#15
Swoopman thanks heaps for your post - very helpful. The EZ Patch stuff looks good and quite an extensive range. Wonder how applying underwater would go though?! My marblesheen (white cement & marble chips but smooth white in appearance) so wouldn't need to paint it which is good.

How did you find applying it? A bit like using mortar mix? On my pool it looks like the walls are noticeably thicker than the corner edges like where I brushed the marblesheen off. So it wouldn't take much of the stuff to patch it.
 

swoopman

Well-known member
Jul 26, 2014
213
Annapolis, MD
#16
Glad the post was helpful. Yes, it is like using mortar mix. The fast set does indeed set very fast.

Bought the fast set because originally planned to do the repairs under water. I found TFP before I did the repair and discovered I needed to do a partial drain to resolve high CYA levels. So I did repairs on the areas that were exposed when the pool was drained but did use the fast set.

As with any mortar repair the prep work is important. The EZ Patch directions call for the repair area to be chipped out 3/8" deep.

One of your posts say the spots are in the deep end but at a quick glance I didn't see how deep that is. I am scuba certified so I had planned on using scuba gear to do the underwater work but as I said I wound up draining instead.

Just guessing based on pics but I would say that the second spot you have, which looks to be the smaller one, is slightly larger than my largest patch. After chipping out per the directions it took a bit of patch material to fill it.

When you're repairing underwater you use less water in the mix. EZ Patch has directions on their site that might be helpful in planning the repair:
http://www.e-zpatch.com/instructions.htm

Let me know any other questions. I'm glad to do my best to answer.