phosphates and algae

[Melba]

Hello all

If this topic has been discussed anywhere else in the forums, please direct me to the thread. We opened our pool last weekend, a 21ft AG round. Mustard algae patches have already returned. My current readings are as follows...

TC >15
FC> 15
CYA 99 too high, I know
pH 7.4
ALK 127

We are hitting it with shock, NOT using any sticks or pucks with stabilizer in an attempt to bring that 99 down. The pool water itself is clear. We run the pump 24/7, brush daily...etc. Last summer I battled the beast with not very good results. I am convinced I am growing a resisitant strain.

When I had my water tested yesterday, an additional test was run for phosphates. It took a little while but I was told that I had a high phosphate level of about 800 ppb. It was explained to me that phosphates act as an algae fertilizer and this might be why I have a resistant and recurrent algae problem. Of course it was recommended I use a phosphate remover but being an avid pool forum reader, I am reluctant to put additional chemicals in my pool.

So I ask your opinions about this. As always, I value what I learn here in the forum.

Thanks for your help!
Melba

[KurtV]

...

We are hitting it with shock, NOT using any sticks or pucks with stabilizer in an attempt to bring that 99 down. The pool water itself is clear. We run the pump 24/7, brush daily...etc. Last summer I battled the beast with not very good results. I am convinced I am growing a resisitant strain.
I think your high CYA is keeping the chlorine from dealing with the algae. With your CYA level, Ben's Best Guess Table (http://www.poolforum.com/pf2/showthread.php?t=365) calls for a shock level of 25 ppm. Stopping the use of the stabilized chlorine (sticks and pucks) is a good start but you're going to have to resign yourself to running a high chlorine level or to a partial drain and refill to lower CYA if you really want rid yourself of the algae.

When I had my water tested yesterday, an additional test was run for phosphates. It took a little while but I was told that I had a high phosphate level of about 800 ppb. It was explained to me that phosphates act as an algae fertilizer and this might be why I have a resistant and recurrent algae problem. Of course it was recommended I use a phosphate remover but being an avid pool forum reader, I am reluctant to put additional chemicals in my pool.
I think you're wise to hold off on the phosphate remover. Chlorine, at the proper level and for long enough, will probably answer quite well. If that fails, several people on the forum have reported success with using polyquat to knock out stubborn algae infestations. I know that Ben touts poly as a better preventative than remedy, but it's hard to argue with success.

Best of luck.

[CarlD]

Hello all

If this topic has been discussed anywhere else in the forums, please direct me to the thread. We opened our pool last weekend, a 21ft AG round. Mustard algae patches have already returned. My current readings are as follows...

TC >15
FC> 15
CYA 99 too high, I know
pH 7.4
ALK 127

We are hitting it with shock, NOT using any sticks or pucks with stabilizer in an attempt to bring that 99 down.

1) As pointed out, you need to run your FC level up to 25 if you want to properly shock your pool. I don't know what you are using that is called "shock"--it could be all sorts of things. Many of the powder packets of "shock" are di-chlor--and they will also add CYA to your pool, making your problem worse. However, cal-hypo and lithium-based chlorinators won't add CYA--but they will add calcium or lithium. Depending on your calcium level, this may not be a problem--I have no idea what lithium does to water. "Shock" could also be liquid shock--usually sodium hypochlorite--same as bleach and sometimes even the same concentration as Ultra Bleach (6%). Liquid chlorine/liquid shock/bleach is normally the best to use with the least side effects.

2) Your attempt to bring the CYA of 99 down will fail. Sorry to be blunt. There are only two ways to lower CYA. The easiest is dilution--drain 50% of your water off and refill and your CYA should drop to 50ppm. You don't want to know the other way..... If you don't want to drain and refill plan on keeping your FC between 8 and 15ppm for normal use. This won't hurt you, but you may see your bathing suits fade a little--that's the worst side effect. If you have Ben's test kit or another FAS-DPD powder chlorine test kit, it's pretty easy to measure chlorine levels.

The pool water itself is clear. We run the pump 24/7, brush daily...etc. Last summer I battled the beast with not very good results. I am convinced I am growing a resisitant strain.

When I had my water tested yesterday, an additional test was run for phosphates. It took a little while but I was told that I had a high phosphate level of about 800 ppb. It was explained to me that phosphates act as an algae fertilizer and this might be why I have a resistant and recurrent algae problem. Of course it was recommended I use a phosphate remover but being an avid pool forum reader, I am reluctant to put additional chemicals in my pool.

So I ask your opinions about this. As always, I value what I learn here in the forum.

Thanks for your help!
Melba

Melba, try the other things suggested first. If you follow them with patience and persistance, they work 99.9% of the time. Only then, when you fall into the that 1 in a 1000 group should you move on to trying things like phosphate removers. They are generally pushed as a hi-tech, quick-fix, but that's just hype. There are no quick-fixes that don't boomerang in some way. I don't yet see any evidence of a chlorine-resistant strain of algae--your TC and FC are too low in relation to your CYA to kill an algae bloom. If after two weeks in an environment of CONSTANT FC=25 (at CYA=99) the algae is still there, maybe then you may need a "Plan B". But you aren't there yet.

The best way to get rid of algae is to extend what you are already doing, as has been suggested. Get FC up to 25, and keep it there, checking 2x to 3x/day and adding bleach as needed, run your filter 24/7. Brush your pool everyday, and vacuum to waste everyday. And be patient and persistent. Remember, if your FC drops too low, you are basically back to square one as the algae will start growing again.

Good luck!

[waterbear]

One final thought for you. Phosphate removers can be a PAIN to use and deal with the aftermath! I would suggest trying them as a last resort when all else has failed as CarlD suggested!

[Melba]

Thanks to you all for the advice!

We are currently using the cal hypo to shock the pool. How do I switch to regular bleach? How much do I use to kill this algae and then how much to maintain once the problem clears?

Is it true that there is a direct corrolation between high phosphate levels and algae....if my levels are as high as they were supposidly tested wouldn't that make my pool ripe for another bloom later?

What will a phosphate remover do to the pool?


Thanks in advance!
Mel

[mkamp1515]

Melba, I recently had a phosphate level almost off the charts (2500). I had no algae breakout so I was lucky. I used a product called "PhosFree" by Natural Chemistry. With my phosphate level so high, I had to use 3 large bottles (3liter each) to remove the phosphates. All you do is put it in your skimmer and run the pump. The pressure on your filter my go up. Mine did but then it went back down. After a few days, I backwashed and repeated the process. Took me about 2 weeks. If your phosphate level is 800, you may only need 1 bottle. Depends on the size of the pool. It will not harm your pool. It will make it look "milky" for a while but that clears up in a day or so (Phosfree looks like milk). Anyway, it worked for me.

Hope this helps.

Mike

[CarlD]

I must disagree. Phosphates only feed algae if it's alive. Kill it, keep it dead, and keep your chlorine levels up so it stays dead and there won't be anything to eat the phosphates.

Phosphate removers should not be used until other methods are no longer able to work. I see no reason to expect our simple bleach method not to work--just because some pool store clerk wants to sell Melba phosphate remover.

Use MWSmith2's free, downloadable Bleach calculator to compute how much bleach you need.

Or remember that 1 gallon of regular bleach (5.25%) adds 5.25ppm to 10,000 gallons of water. 1 gallon of ultra bleach (6%) adds 6ppm to 10,000 gallons. Adjust your bleach based on that, how many gallons you have, and how high you are pushing your FC level.