Help - solar cover = algae?

Hi all, I've got a strange problem! I opened my pool two weeks ago, and because I jack the clorine up to 6 or 7ppm before closing, the pool water was pristine. I brushed up some algae on the sides that must have been missed, and also must have been dead because it didn't spread, correct? So, I've been keeping the TC = 5 or 6, And that has been almost all FC, less than .5 CC. PH is 7.6, ALK 100, don't know what the CYA is (waiting on reagents). There is no calcium, it's a vinyl AG pool. So, I get a new solar cover, and last week, put it on. I haven't gotten my mail order reel yet, and the water temp is mid 60's so I just leave it on 24 hours a day for 5 days. I just peeled it back to look and take a sample, and there is green algae on the sides!! Not alot yet, but some enough. Water is still clear. What would cause this? Last year, it seemed that the solar cover was a harbinger of algae, but I just figured I wasn't keeping a good enough eye on the balance. This year, I know I've kept the CL at 6 or so. I had the pool store check the CYA, said it was less than 10, and bought enough to bring it to 40, only put in enough to bring it to approx. 20, because again, I don't trust them, and want to check for myself. please help with any suggestions!!

Kevin, I'm not a chemist (... but I play one in pool owners' backyards for a living ;) ) I can't properly remember how it works, but I recall reading on the 'old forum' about needing to 'gas-off' the byproducts of chlorinating. Whether or not failure to do so will cause an algae outbreak, I can't recall. To gas-off a pool you do need to remove the solar, or retract an auto cover for an hour or so a day. If you didn't do this for a few days at a time, it could be the reason for the "solar cover/algae corelation". I'm sure someone else here can tell you the process better.

You never got rid of the algae you started with. If there's algae in there when you open, it's not dead unless you shocked it dead before opening. Putting the cover on warmed the water and accelerated the algae's growth.

I shocked it, and cleaned it prior to closing. When I opened, water was crystal clear, and only found a couple of spots of algae on the walls that I'm positive was missed when I swept. It should have been dead because I shocked it, correct? Also, if it was live, I'd assume that I would have opened a pool that resembled a swamp? I live in Georgia, so winter temps range from higher 20's some nights, to 50's and low 60's for highs. I don't think the water temp ever gets below 45 or so. thanks.

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Originally Posted by waste

Kevin, I'm not a chemist (... but I play one in pool owners' backyards for a living ;) ) I can't properly remember how it works, but I recall reading on the 'old forum' about needing to 'gas-off' the byproducts of chlorinating. Whether or not failure to do so will cause an algae outbreak, I can't recall. To gas-off a pool you do need to remove the solar, or retract an auto cover for an hour or so a day. If you didn't do this for a few days at a time, it could be the reason for the "solar cover/algae corelation". I'm sure someone else here can tell you the process better.

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Thanks. I'm sure there is some correlation, and you may be on target! Need to get a reel, but for 24' pools, they aren't cheap!

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Originally Posted by kevincad

It should have been dead because I shocked it, correct? Also, if it was live, I'd assume that I would have opened a pool that resembled a swamp? I live in Georgia, so winter temps range from higher 20's some nights, to 50's and low 60's for highs. I don't think the water temp ever gets below 45 or so. thanks.

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One shock dose won't kill algae. Water temps below about 60 just put the algae on hold until it's warm enough to grow.

I agree with John that one shock dose won't usually kill algae. But, there have been several people on the forum (including Poconos and me) that had some very slight issues with algae this winter when the water temp was below 50. (We used to tell people that below 50 they didn't have to worry about algae, but we found out that is not always true.)

Watermom

I had this exact same problem 2 times last summer with my cover. I assumed that my cover itself was "contaminated" with with live algae after being off for a while, so that even though the pool itself was clean, it started to grow into the pool. And the pool gets much warmer with solar cover. (Your cover was new, so my theory doesn't seem to work so well.)

This year, I'm going to try to rinse off the cover really well before putting it on. I'll also not use the cover if the water gets to the high 80's.