Algae won't leave... what kind is it?

[plcguru]

Hi,

Had this algae the end of last year. It never really left. Opened the pool this year and the fun begins again.

Currently my pool is:

CYA 100
pH 7.3
TA 110
FC- 2 days ago I shocked it to 27. Today it was 21.5 . I just now shocked it to 37 hoping that will kill whatever kind of algae it is.

Any idea what kind of algae it is? I brushed it and nothing happened to it
I appreciate any advice you experts can supply!!!

Incidentally, I use the BBB method :)

Here are some pictures of the problem:
http://www.melore.com/ebay/tools046.jpg
http://www.melore.com/ebay/tools047.jpg
http://www.melore.com/ebay/tools048.jpg

[chem geek]

Welcome to The PoolForum! :)

That looks like yellow/mustard algae to me, though it could be pollen. If it's yellow/mustard algae, then it will tend to grow in shady areas of the pool, including on the walls and it will act like dust but will feel slimy. If it's pollen, then it will tend to settle to the bottom in areas where circulation has things settle and will feel squishy. Looking at a sample under a microscope is pretty definitive since pollen is solid and often spiky and round while the algae is often oblong and semi-transparent where you can see the interior.

Yellow/mustard algae is more resistant to chlorine and most certainly your 2 ppm FC with 100 ppm CYA isn't even enough to prevent green algae let alone yellow/mustard algae. I suspect you are using Trichlor tabs/pucks that got your CYA that high -- it could even be higher than 100 ppm. You need to get your own good test kit, the Taylor K-2006 you can get here (http://www.amatoind.com/taylor-k2006-test-p-555.html) if you do not have one.

I would first of all dilute your pool water to lower your CYA level since it's hard to manage a pool at such a high CYA level since it requires rather high FC levels to prevent algae growth and even higher levels to shock the pool to get rid of such algae permanently.

Let's say you get your CYA lower to 50-60 ppm. Then, you would need to supershock the pool to around 30 ppm using chlorinating liquid or bleach you add slowly over a return flow at the deep end with the pump running. You maintain this high level until 2-3 days after the algae is no longer visible. You also need to get behind light niches and under removable ladders to expose the algae that is likely there as well (remember it likes shade and such areas don't get good circulation of chlorine) and you need to put into the pool everything that gets into it -- poles, nets, brushes, pool toys, etc. so that you don't reintroduce the algae later on. You also need to wash your swimsuits thoroughly with soapy water.

Once you get rid of this algae, then you can maintain normal chlorine levels according to Ben's Best Guess CYA chart (http://www.poolforum.com/pf2/showthread.php?t=365) where you will note that the minimum FC is 8 ppm for a CYA of 100 ppm -- instead you'll likely have 50 ppm CYA so a minimum FC of at least 3 ppm at all times.

[plcguru]

Hi,

Sorry for the confusion on the FC. 2 days ago I shocked it to 27ppm. Today it was 21.5ppm. Tonight I shocked to 37ppm. So, it hasn't been less than 20ppm for a couple days.
I test with the TF-100 and Taylor K-1000.

I scrubbed the algae with a brush on a long pole and there was no change. No dust or anything. No change at all. It remained as it was. Is it pollen then?

How would I get rid of pollen if it is that?

The algae or pollen is at the bottom of the deep end on the floor, none on the walls. None in the shallow end or anywhere else(it's a true-L shape pool). The pool is full sun(no trees at all) and been open for about 2 weeks. The rest of the pool looks fine and has no algae or pollen.

Yes, I used trichlor pucks for the first 8 years and have been using BBB starting mid-last year. I will drain alot of the water as the season progresses since the CYA is so high.


How would I get rid of pollen if it is that?

Thanks!

[chem geek]

So you brushed this fairly vigorously and it doesn't move at all? If that's the case, then it's unlikely to be either algae or pollen (only black algae would tend to stick to the floor or walls so tightly, especially in plaster) so perhaps this is metal staining.

Is this a plaster surface (as opposed to vinyl or fiberglass)?

If this is staining, then it could be an organic stain, say from tannin from leaves sitting on the bottom, or it could be metal staining. If this is a plaster surface and you take a Trichlor puck and put it over one of the stains, then if it's organic, it will lighten up and go away (do NOT do this if this is a vinyl surface -- the acidity of Trichlor is VERY bad for vinyl). If it doesn't, it's more likely to be a metal stain. If it's a metal stain, especially an iron stain, then putting ascorbic acid (say, a Vitamin C tablet) on the stain would have it fade.

So you have some things to try, but if your high chlorine isn't changing the situation, let the chlorine drop back down. Measure your FC level tonight and then tomorrow morning before the sun hits to see the rate of FC drop. If there is a lot of algae or even pollen, then the FC can drop overnight, but with stains it usually doesn't.

Your pH measurement won't be valid at high FC levels.

[plcguru]

Hi,
It's a vinyl liner.

My shocking to 37ppm seems to have made the stains worse :o

If it made the stain worse I would guess my pH is higher than my test result (due to high chlorine level) and the shocking with adding even more chlorine caused more metal to fall out of solution and make the stains worse.
Correct? If it were organic the shocking would have made it better...

I crushed some 1000mg vitamin c (maybe 12 tablets) in a sock and rubber banded the sock to the end my extendable pole I use for skimming/brushing. I scrubbed the stain (again, it's in the deep end) and no change. I put a chewable tablet (500mg) on the stain and left it there for the night.

I also had a stain from my daughters hairpin that fell out of her hair and caused a rust stain in the shallow end. I scrubbed that with the Vitamin C and no change. I also left a vitamin c tablet on that overnight and will check in the morning if it is gone (or even if the tablet dissolved)

Just for kicks(?) I rubber banded a Mr Clean magic eraser to the end of the pole and scrubbed the yellow spot in the deep end... no change.

Any thoughts on what's going on here???

Thanks from a newbie :D