Hi All,
Thank you all for the information in these Forums! I have a algae problem that I just can't get a grip on. I've read and tested and learned that this can be quite a balancing act in the beginning of the season. We had a 'pea soup" pool from the winter so the entire pool was drained, scrubbed and refilled about 5 weeks ago. It was shocked, balanced and maintained. Algea showed up last week so I added bleach to 15ppm and kept it there for 48hrs. brushed 2-3 times a day added bleach etc. so yesterday I have cloudy crappy water with that irritating teal-green haze. I have been on the pool calc and with my numbers it suggests shock to 29ppm. I have the good test kit ordered and in the mail but for now I'm using the 6 way strips and a cheesy OCO/PH kit. Heres my #'s
So do I need to shock to 29 with a vinyl liner as the calc suggests? Thanks in advance for having to repeat yourselves so often :oops:


TFP Expert
Platinum Supporter
LifeTime Supporter
May 7, 2007
Silver Spring, MD
With CYA at 50, shock level is 16 (or 15 depending who you ask). The higher shock level of 29 is for persistent mustard algae. If you think you have persistent mustard algae you should shock to 16 till the water is clear and then shock for one additional day up to 29. The higher FC level for just one day won't do anything significant to the liner, but you shouldn't keep FC that high for very long.

It sounds like you are already able to kill off algae, and it will stay gone for a while, several weeks the first time and perhaps a week the second time. That suggests to me that you are not maintaining the proper FC level during normal day to day operation. With CYA at 50, the normal day to day FC level should be between 4 and 8 and never below 4.
:-D Thank you for the prompt reply Jasonlion, and you are correct about the FC level, I was keeping it about 3 (suggested safe level on cheesy OCO/PH test chart :hammer: ) but have noticed on pool calc that I should keep it higher. Will shock to 16 and keep it there until problem is resolved.. Thanks again!!