3 Years of Algae

Hi all, have been battling algae for 3 years now. Always did what pool store recommended, would not see if for a few days then bam back again. Same thing all year this year until I found this site. My water looks FANTASTIC, best it has in years however....I still have not passed an overnight chlorine test. I have been slamming the pool but I suspect my trouble is behind my light. Am working on getting that out and cleaned. When I went out there this morning I did once again see a small spot of algae. Test results are as follows.

PH 7.5
FC 33
CC 0
TC 33
TA 110
Cyanuric Acid-80

I have been shocking up to mustard algae levels according to the chart. First night chlorine took a nose dive, brought it back up and it lost about maybe 3 or 4 ppm overnight. I have a lot of gray stuff on the bottom of the pool that I am guessing is dead algae. Let it slack until I can get my light out, seems to be stuck then will bring it up again. Do I seem to be on the right track? My CA is high I know but I hope to get through this year (closing in two weeks) and will drain at beginning of season next year. Any advice would really be appreciated.
 
Welcome to TFP! :wave:

Be sure to brush regularly since it sounds like you might have poor bottom circulation if you are seeing algae at high chlorine levels. Also, if your water is now clear, clean/backwash your filter if you have not already done so since dead algae in the filter will have you fail the OCLT. Also, the OCLT criteria is for regular shock level, not yellow/mustard algae shock level. You may lose somewhat more, though probably not 3-4 (more like 2). Also with your high CYA level you may also lose more overnight (chlorine oxidizes CYA). The bigger issue at this point is the visible algae so yes, get behind the lights to see if that is a continuing source for algae since you want to kill it off, especially if it's yellow/mustard algae.
 
Thank you for the quick reply. Just managed to get the light out as per my suspicion the back of it does have green on it. Will get that taken care of clear out its little house in the pool and bring it back up to shock levels and see where that gets me! I will also brush diligently again. I am going to pull my ladder out since right underneath that is where I saw the algae spot. I will vacuum tomorrow to get all that gray stuff out and do a backwash.
 
If the ladder has water inside it, there could be a harvest of algae inside it. Inspect the ladder the best you can for algae and you might have to remove it once in a while to give it a good scrubbing. Algae likes to grow on surfaces that don't get brushed.
 
i do suspect algae inside ladder thats why i will pull it out. will just wiping light down with bleach be sufficient to kill all the algae? i plan on leaving light out overnight as well to expose its case inside pool to shock level of pool water. am i on track with this plan?
 
Yes, exposing the light niche to shock levels of chlorine will be good. Leaving the light out in the water exposed to shock levels of chlorine is also good. Standard pool lights have water behind them intentionally. It's used for cooling the lamp, but the circulation is poor.
 
Light wasnt as bad as i thought but it did have some really dark green patches on it. bleached it let it sit for a couple of minutes then did it again. three times i did it. have robot in pool as well now letting him get cleaned up. there was quite a bit of gray stuff behind the pool light, not sure what it was but i cleaned at that area out good as well with brush. hopefully i am on the road to recovery. but with chlorine at 33 ppm this morning how come i saw a small green patch by ladder. its been fine for over a week and a half. i didnt expect to see any growth until chlorine fell way down. also with the algae behind light would it typically start to bloom by the light first or could it really be anywhere?
 

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Biofilm is what forms when bacteria excrete chemicals that protect them from the environment and becomes more chlorine-resistant as a result. Biofilm can be a combination of different microorganisms. If you kill the microorganisms before they form biofilm, then it will not form, but if a pool isn't maintained properly, especially over an extended period of time, then such biofilm has to be physically removed -- chlorine alone won't handle it (except at extremely high levels).
 
A slimy surface that grows and is not inhibited by chlorine. Usually it's clear or light gray and not green. Green usually indicates chlorophyll so either algae or possibly green sulfur bacteria or cyanobacteria.

Regardless of whether you have biofilm, grease, or anything else slimy on a surface the solution is the same which is to physically remove it. If you had a very serious amount of biofilm or white water mold in the pool developed over years of improper management, then you could use a powerful surfactant to help remove them, but I don't think we can conclude this yet.
 

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