Best Shock for Algae

[polyvue]

Well, the spots are still there and I am still debating what the heck it is. I did shock it with 3 gallons of bleach a couple of weeks ago. The spots were and still are unchanged. At least they havent gotten any bigger or multiplied. I was out of town for a few days and was just able to test my water a minute ago. I used the Taylor K-2006 test kit.

FC - 2ppm
CC - 0
PH - 7.8
ALK - 110
CAL - 270
CYA 80

I struggle with the CYA test. Do you drop until the black dot is really completely gone? It seems I can always make it out a little ... This time I just added until my hubs couldn't see it!

The spots are still there because 3 gallons of bleach was not enough to shock a 25K gallon pool. That would just get you started... some algae will only respond to VERY high levels of chlorine over an extended period.

And having that level of CYA (80 ppm) in your pool works against you when you're trying to get rid of algae.

If you type the results of your most recent test into a calculator, you'll see what I mean.

http://poolcalculator.com

If possible, drain some of the pool water until you can get CYA down to 30-40, ideally. Otherwise, shocking will require 20-40 ppm of chlorine -- perhaps more, over any number of days. That's a lot of bleach!

To effectively rid your pool of the algae, prepare yourself for a multiple day attack. Buy twice as much bleach as you'll think you need. Buy that stainless steel brush and use it. It should be OK with gunite and it's meant to be abrasive. But any brush is superior to not brushing.

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"It actually looked like a rust stain at first then morphed into what looked like a clot of dirt stuck to the bottom then it started spreading. I am assuming it's black algae but the color is still rust so maybe mustard algae."

Sure doesn't sound like green algae. Recommend using amount of chlorine appropriate for mustard algae.

Start by dropping your pH to around 7.4. Do this because the chlorine will be more effective at a lower pH level and it will be impossible to test it in the days that you'll be shocking the water (the chlorine affects the phenol red pH indicator in Taylor kits).

Then hit the pool with a dose of chorine that will bring it to shock level ALL AT ONCE. If you can do it in late afternoon or evening, all the better. Test the chlorine every few hours and first thing in the morning and KEEP adding chlorine to maintain shock level until there's no more than about 1 PPM drop in FC from midnight to dawn.

If possible, run the main filter pump 24/7. The entire process could take a few days... to a few weeks. Some species of algae can survive high levels of chlorine for days or months which is why you must....

Brush at least once every day.


Clean the filter cartridges once this is all over to be sure nothing is lurking in there... and thereafter increase your minimum FC level to 10-15% of CYA.

Example CYA 50 PPM x .10 = FC 5 PPM


Best of luck to you!


Oh yes, check out these pics of the CYA test at Taylor's website, linked below. The black dot really does disappear.

WHY MONITOR CYANURIC ACID?
https://www.taylortechnologies.com/C...P?ContentID=44

[spatt]

I'm sorry I am quick to respond but I do read posts as soon as they come up and put the advice into action.

I could drain some of the pool but not half as the pool calculator states.

I am lowering my PH today and adding bleach tonight.

Wish me luck ..

[spatt]

I decided to do a partial drain to get my CYA down before shocking. This took a few days to accomplish because my husband had to track down the pumps. The CYA is still at 60. I guess since the pumps are still here, I will drain again, re-adjust PH to 7.4 and shock. The pool calculator is a GREAT TOOL! I had never seen it before.