Freaked Out by ALgae Help!

[CarlD]

120 is a VERY high CYA.

You need to add bleach until your FC level is 25ppm, and keep it there until the algae is dead and your water is clear. (This is called shocking)

Then you need to keep your FC level between 8 and 15ppm all the time.

Alternatively, drain half your water and refill to lower CYA to 60. Then shock to 15-20ppm and keep a maintenance level of 5 to 10ppm of Free Chlorine.

Oh--and NEVER trust a pool store that says a CYA of 120 is low! 20 is low, 120 is too high.

[mysticgraces]

Sorry folks..I added a 1 by accident to the CYA..its actually at 20 and NOT 120 DUH! and hres the really stupid part..when I looked again at the bottom of the pool the spots look like SAND..its grey,not green (we have a blue liner,hence the colour blindness) so I suspect the filter is spewing out sand...I noticed it once before after we vacummed the pool..

[circlenranch]

Well that makes a little bit of a difference With a CYA of 20 your FC is just right at 4 ppm. Now the sand bit I don't know about, we have a CART filter.

[CarlD]

CYA = 20?

Ok, shock to 10 or 12 and hold it there until algae is dead, then maintain between 3 and 6ppm.

You should raise CYA to 30 or 40--Use 1/3 to 1/2 of what you calculate you'll need to get it there.

Or you can use Tri-chlor pucks/sticks --they'll add it.

[gordyjamz]

Sounds like you have mustard algae. Its brown and looks like sand. Sits on the bottom of the pool in spots about htes size of a quarter. Sound like your problem? I don't think its sand since you stated that it disappears when touched. Sand doesn't dissolve, so it wouldn't do that. This algae seems bloom right after a good rain. You need to shock like they say here and hold it there for a couple of days or even a week until the algae doesn't return anymore. Also need to vacuum that stuff to waste to get it out of your pool. To keep it from coming back in the future, I would shock every time after a good rainfall.