My first mustard algae

[kjcole]

Well, things conspired against me and I had to leave to pool unattended for a few weeks. A light dusting of mustard algae on the bottom greeted me, despite my SWCG keeping around 4 ppm chlorine.

After measuring my CYA my mustard algae shock level (from the table here) was suggested to be 39!! So, off the Walmart for bleach. I dropped my pH to 7.2, raised my FC to 35, plus I dumped in a few ounces of some non-foaming algecide (HTH) I found at Walmart. I brushed the sides and bottom and attacked the area under the steps as well. Plus I tossed in all the floats and toys.



I must have hit the pool chemistry like a sledgehammer because the bottom cleared literally within 3 hours. Ran the pump overnight with the SWCG running at 40% also. Then went back to my normal 8AM-7PM hours.

Over the next three days I allowed the FC to drift down to about 13, where it is now. Brushed each day, backwashed filter yesterday. Never recorded any CCs during this process nor any FC loss overnight (once I went back to my normal filter hours, so the SWCG wasn't adding FC overnight).

Today
FC 13
borates - 50 ppm
TA 130
CYA 55
pH 7.3


So far, the pool is spotless and sparkly. I will maintain FC around 10 through next week and then let it drop back to 4-5 for the rest of the summer.

Am I doing this right?

Kelly

 

[reebok]

your cya is too low for your swg (according to best practices). are you sure it wasn't just dirt?
pool-school/water_balance_saltwater_generator

 

[kjcole]

I had added stabilizer a few days before which should be raising it to 70, but it must still be dissolving. I'll test in a few more days so I don't over stabilize.

This was definitely mustard alge - dirty brownish, greenish, with a hint of yellow when viewed under a magnifying glass, and dispersed like a cloud when brushed. Skimmer sock had a greenish tinge. 'Dirt' reappeared over the bottom and steps overnight twice after meticulous vacumming. This convinced me it was an algae bloom. Hasn't reappeared since the first day of shocking, so it must not have been dirt.

Kelly

 

[Brad S]

IMO, your cya is fine. Since your shock level for mustard is 39, it would be a lot higher if your cya was 80! As i said, i dont agree with the cya being at 80 for a swg. It makes your shock level astronomical, and if your run your pump for a proper amount of time and have the swg sized properly, you shouldnt have any problems. A cya level of 80 is ridiculously high, IMO, no matter how your chlorinate.