Algae is driving me nuts

[shadowman]

Well, we left on a short vacation, leaving instructions with our son to test the water and report the results. The next day he said the chlorine was down to 10 and there was no brown stuff in the bottom. The chlorine held the next day and the bottom was clean. When we came home today it looked beautiful and I tested and the numbers were:

FC = 5
CC = 0
PH = 7.4
TA = 90
CYA = 80

I just went out to put the solar blanket back on and was shocked to see the yellowish brown stuff back in the shallow end. I am close to ordering several truckloads of dirt to fill this thing in. I guess it's back to shock levels. Any advice?

[mbar]

With your cya 5 is your minimum chlorine level. I would suggest you take it back to shock and keep there for a couple of days. When you hold the chlorine overnight, you can start to let it drift back down, but keep it at the high side of your chlorine level which will be 10ppms for a couple of weeks. This way any algae that is just starting will get killed off - if the chlorine levels are too low, it is easy for it to get a foothold again Give a good dose of high chlorine and get rid of it once and for all

[chem geek]

If this "yellowish-brown stuff" is yellow/mustard algae, then instead of a minimum FC level of 7.5% of the CYA level (which keeps away green algae), it takes a minimum FC level of 15% of the CYA level to keep this algae away. At a CYA of 80 ppm that's an FC level of 12 ppm to keep this algae away from being reintroduced.

Also, the shock level for yellow/mustard algae is higher than for green algae, but with such a high CYA level it's probably impractical. You should also make sure that the yellowish-brown stuff isn't dirt or pollen though it does sound like algae.

Richard

[Wayne LaBanca]

If this "yellowish-brown stuff" is yellow/mustard algae, then instead of a minimum FC level of 7.5% of the CYA level (which keeps away green algae), it takes a minimum FC level of 15% of the CYA level to keep this algae away. At a CYA of 80 ppm that's an FC level of 12 ppm to keep this algae away from being reintroduced.

Also, the shock level for yellow/mustard algae is higher than for green algae, but with such a high CYA level it's probably impractical. You should also make sure that the yellowish-brown stuff isn't dirt or pollen though it does sound like algae.

Richard

I'm fighting the same battle, vacummed to waste last night and shocked for good measure. Today at noon the brown on the bottom is back but not as bad. Are you saying that the CL level should always be kept at 15% once Mustard Algae has been present?

Wayne

[chem geek]

Unless you completely shock the pool at high levels (60% of the CYA level for 2-3 days) and do not have yellow/mustard algae reintroduced into the pool (via bathing suits, poles/brushes, etc. so wash the former in hot soapy water and put the latter items into the pool while shocking), then the higher maintenance FC isn't necessary. But if for whatever reason the algae is put back into your pool, then yes, keeping the FC at 15% of the CYA level has been the point which keeps it from growing, based on several user reports so far over more than a year.

I'm going to write to Buckman Labs for any info on whether PolyQuat 60 inhibits this algae -- we know it's good for keeping away green algae, but so is maintaining chlorine levels. Though higher levels of chlorine will keep yellow/mustard algae away, perhaps a little assistance from an algaecide would be an option. I'll let y'all know what I find out.

There was one report on another forum of copper sulfate getting rid of this algae, but we all know the side effects and downsides of copper so that's why I want to see if our stalwart PolyQuat 60 will do the trick for those that don't want to maintain the higher FC level or just want extra insurance.

Richard

[chem geek]

I received a response from Buckman Labs and PolyQuat 60 will be effective at inhibiting all the common forms of algae -- green, yellow/mustard, and black. It may take different levels to inhibit different forms, but we are restricted to the dosages recommended on the bottle so basically I say that if you want to try that, you can see if it works to inhibit yellow/mustard algae in your situation. You could even use less than the recommended amounts if you want to see if the threshold is lower, but I suspect that the threshold is only lower for green algae, not for yellow/mustard. By law, you are supposed to stay within the dosages recommended on the container label, but I think there should be no problem trying less -- the main issue is that using more than the recommended amounts doesn't meet the safety standards that were proven to the government during registration while going lower may not meet the effectiveness standard which we are less concerned with IF a lower level is still effective for our needs.

I would also guess that having the chlorine level at the normal target to inhibit green algae may allow for somewhat less PolyQuat 60 to be needed since the combination could be somewhat additive in terms of prevention of algae, but again that's something for you to try. Carl, for example, keeps his FC level at normal targets, but uses a small amount of PolyQuat 60.

Be sure to let us know how it works out if you try the PolyQuat 60.

Richard

[shadowman]

Thanks Richard. I have a quart of PolyQuat 60 but I haven't used any yet. The pool has been sparkling all week since my last shock. We have had very hot weather, over 100, for a few days and the chlorine is staying very stable. I add a little 6% bleach every other day and the numbers are holding nicely even with the blanket off. I will continue to keep you posted.