Hey Y'all, I'm back.

My pool has been the most awesomest thing ever since I converted it .

I recently bought a solar blanket on Sunday. I put it on, and two days later I got some algae growing. I dont know if their related, but I'll post some test readings in a little while.

My chlorine levels have been normal.

Should I bring the FC's up to shock level?

Anytime you have visible algae, you should shock your pool. Remember, it is a process....not just one dose.

What are your test results?

I agree w/duraleigh. If you have visible algae, shock it

Total Chlorine 8 ppm
FC 8 ppm
pH 7.3
Alkalinity 55 ppm

These are my readings as of now. I just added enough chlorine to bring the FC up to 15.
I bought some "stop yellow" at the pool store because the guy said it would get rid of quicker. Is this true, or should I take it back and get my $10 back for more chlorine?

What about the correlation between the new solar blanket and the arrival of algae? Does anyone know if one has to do with the other? Maybe it's a coincidence or a cause.

Maybe I missed it, but what is your CYA level?

I suggest you only use chlorine to clear your pool.

Adding other products can create another set of problems. I'd swap the 'yellow' stuff for LQ.

Sorry, CYA is .5
What is LQ?

LQ=Liquid chlorine. I was trying to run your numbers through the pool calculator and its not adding up. Do you test yourself or do you take the water to a pool store? It would be very difficult to get a .5 reading for CYA. Do you know your pH? Also if your pool is 24 ft by the usual 4.5 deep it would be around 15200 gallons according to the pool calculator. That may be throwing the results off too! If you can run a fresh set of tests and post them and tell us what you are using to test with we should be able to give you better advice.

I have a 24ft round 52 wall and my gallons is 13,500.

It's a coincidence-not the solar cover. I leave my cover on all the time and never get algae.

Your CYA is .5 - that result isn't possible, the tubes stop at 20 or 30.....??? Did you ever test your CYA level after you added it following your conversion?

It's possible the cover had algae or other organics that increased the chlorine demand significantly and had the chlorine level drop too low (relative to the CYA level) and the warmer water temperature would accelerate algae growth, but ultimately the algae was able to grow faster than chlorine could kill it because the FC/CYA ratio got too low. To prevent this in the future, if one is going to put on a cover that isn't known to be clean, one can either clean it first or raise the chlorine level in the pool before putting on the cover and then test more frequently until the chlorine usage rate stabilizes.

Richard is correct - but since you stated the solar cover was new, I wouldn't place the blame on the cover in this particular situation.

Sorry,
CYA is 60
pH is 7.3
Alkalinity is 75
FC right now is 12.5, gonna top up to 15 in a minute.
Water looks like it's getting greener.
I'm using a TF-100 test kit.
My water averages 47" deep.

If your CYA level is 60 - your shock level is now 24 - not 15. (15 was just for the conversion.) Now that you have CYA in your pool you need to maintain the levels according to the CYA chart.

Why does the pool calculator show my shock level to be 18, and the CYA chart shows 24?

I'm not adding my voice here because I know the answer; in fact, I've often noticed that there's sometimes a discrepancy between the CYA chart and the Pool Calculator's suggested shock level. The latter seems to suggest a normal shock level of 30% (of CYA) whereas the former is roughly 40%. I'm sure chem geek and/or JasonLion can clear this up for both us.

Well, sometimes they agree to disagree: Re:Pool Calculator shock level vs. CYA/Chlorine Chart shock level



To add a personal note, the higher shock level should work a little faster.

Ben Powell's original Best Guess CYA chart has higher shock levels at low CYA and lower shock levels at high CYA compared to my Chlorine/CYA Chart. Ben's chart was based mostly on his personal observations and experience while I started with his data but made it consistent with chemical theory in terms of the active chlorine concentration. His min/max columns were more consistent to the FC/CYA ratio than the shock column. I also added new min levels for SWG pools and shock levels for yellow/mustard algae based on reports on the forums.

For minimum chlorine levels the prevention of algae is a fairly clear delineation with the upper limit mostly dependent on the maximum rate of algae growth limited by temperature and sunlight (assuming plentiful nutrients). The shock level, on the other hand, would just affect the rate of clearing of the pool so isn't such a clear cut delineation.

Richard