Mustard Algae

[tnalaskan]

First, let me say I LOVE this site. It has helped a newbie tremendously. We have a 27ft ABG pool. It took 17,300 gallons to fill it up. Used it for about 6 wks last year as we bought late in the season. When we opened it this year, no problems. Until now. We definately have/had mustard algae.

For the past 4 days I have kept the FC levels above 20ppm. Water is clear now but still has some brownish spots on the bottom. Have vaccuumed and brushed the sides. We run the pump, a 1.5hp pump on low 24/7. On high for 2 hours after adding the liquid bleach. Tonight my levels are as follows (no 6% bleach added since last night):
FC 26 CC 0 ph 7.2 Alk 75 CYA 80 I test with a Taylor K-2006 FAS-DPD kit (which I love).

Have I left the chlorine levels up long enough to kill the mustard algae? Should I now keep my chlorine levels above 5-7 ppm? Should I add polyquat when the chlorine drops back down some? What about flock? Should I soak all the noodles, floats, vaccuum hoses, etc in bleach before putting back in the pool?

Sorry for the long post with so many questions but I just do not want the algae to come back. Would like to enjoy the pool since it is the perfect weather for it. Thanks so much in advance for any help you can give me with these issues.

Tnalaskan

[aylad]

With a CYA of 80, keeping your chlorine levels in the 20s is nowhere near high enough to kill mustard algae. See the "best guess chlorine chart" linked in my sig for more information about where your chlorine levels need to be. If you still have brownish spots on the bottom, then it's not dead yet. You need to raise the chlorine according to the chart, and hold it until those brownish spots are gone. You do also need to soak all the stuff that was in the pool before putting it back, so you don't add the algae back to the pool. You can put it all in the pool while you're holding shock level if you want, and kill both of those birds with one stone.

[tnalaskan]

Are you saying I should raise the chlorine to 75? Should I run the pump on low or high?

[aylad]

Yes, if your CYA level is 80, then Ben's recommendation for mustard algae is 75 ppm. Note that it can cause some liner fading, and pretty much will make the pool unswimmable until the shocking is over, because that level of chlorine will be irritating to swimmers and their suits.

I would keep the pump on low so that it doesn't drive the algae back through your filter and back into the water.

[tnalaskan]

Thanks. I added more bleach. By my calculations it should be at 71ppm. Since the cholorine tabs are keeping the CYA up, will just using bleach instead of the tabs eventually lower it?

[chem geek]

Using bleach instead of tabs will prevent the CYA from continuing to rise. The CYA may drop if you've got water dilution such as from backwashing or from rain overflow (if it rains this time of year where you live) or carry-out and splash-out. For getting rid of yellow/mustard algae it is very, very important that you kill all the algae in the shady places it likes to hang out. That includes getting behind light niches and under removable ladders. Put in all equipment you use for cleaning into the pool during the shock process (i.e. pools, brushes, nets, etc.).

[tnalaskan]

I found the pool calculator in regards to how much bleach to add to raise the levels to 75. Thanks for your help. I really do think this is the best site for all of anyones pool needs and questions. Now back to Walmart for more bleach.

[Watermom]

I really do think this is the best site for all of anyones pool needs and questions.

Thanks! So do we!

[tnalaskan]

The pool is crystal clear now. Have kept the chlorine levels up where reccomended. My problem now is there are still a few small spots of the brown on one side of the pool. I know I have to keep the levels up until all gone. I have ordered the reagents for my Taylor K-2006 kit but they will not be here until at least Tuesday. I don't have enough left to see how high the levels of chlorine are today so I don't know how much bleach to add to keep it at 75. I have phoned everywhere I know to phone in this area looking for reagent. No one has it. Does anyone know of anyplace that has the reagents in the Chattanooga/Cleveland TN area? If not is there another way anyone knows of to test for the level of chlorine? I would hate to have to start all over.

[Watermom]

I doubt you'll find it locally. Go ahead and order and maybe pay the extra $$ for rush shipping. In the meantime, keep adding bleach.