Shocking Questions

[yossarian]

So I thought I might have mustard algae as I had two yellowish deposits on the floor of the deep end. I had been keeping my solar cover on, 24/7 as I was working and no one else was home, so I figured that didn't help matters as far as mustard algae was concerned.

In any event, I shocked my pool last night to 24 (based on a CYA of 40, which is a bit higher than my last reading of 30, but I don't have confidence in my last reading as it was 50 2 weeks ago).

This morning, I tested and was at 21.5, which was a 2.5 drop, but with no CC.

I brushed everywhere and the pool is definitely cloudy and I can see quite a bit of whitish residue. Is this probably algae? I can see the floor of my deep end, which is at least 10 feet down, but not as well as I usually can.

Also, I found a mouse and 2 frogs in my skimmers, would that have been enough to also cause my FC to drop in addition to algae? I forgot to check the skimmers last night, but the creatures were not there for more than 24 hours.

Should I keep my solar cover off until eveything clears? I hate to lose the warmth and chlorine. Plus, I have a clear cover, so it does a decent job of absorbing sunlight.

By the way, here are the last test measurements I had:

FC - 21.5
pH - 7.6(?) -- It was hard to tell and I understand the pH test might be unreliable if FC is over 10.
TA - 110
CH - 350
CYA - 30 (as I stated, it was 50 2 weeks ago, so I have my doubts about this measurement)

 

[Bama Rambler]

You need to hold it at shock level for your CYA (I'd use the 50 ppm number) until you pass the OCLT. Once that's done you can concentrate on everything else.

 

[yossarian]

Thanks. How do I know if I had mustard algae. I thought I read that most people are incorrect in that diagnosis.

 

[Bama Rambler]

With Mustard algae, it'll go away when shocking but come back under normal FC levels. That's when mustard algae shock is required.

 

[yossarian]

With Mustard algae, it'll go away when shocking but come back under normal FC levels. That's when mustard algae shock is required.

I assume that you mean the shocking level specified for mustard algae? Otherwise, if you shock to the general recommended level, will the mustard algae remain?

 

[Bama Rambler]

I didn't make that clear did I!

With Mustard algae, it'll go away when shocking to the normal algae level but comes back under normal FC levels. That's when mustard algae shock level is required.

 

[yossarian]

I didn't make that clear did I!

With Mustard algae, it'll go away when shocking to the normal algae level but comes back under normal FC levels. That's when mustard algae shock level is required.

Got it, thank you. The thing is I don't know if I had mustard algae or not. I saw two brownish yellow spots in the deep end. I cleaned my filters with a hose and the ground turned light green with shades of yellow on some of the borders. Otherwise, the pool had a faint whitish residue that I guess was algae. But it almost looked like any other undissolved powder you add, just covering the entire floor. But the water itself was clear until I shocked, and presumably killed the algae.

So do I suck it up and shock all the way to 29 for mustard algae (assuming my CYA is 50)? Or do I see what happens with standard shock levels first and see if anything appears once I pass the overnight test and drift pack to normal FC levels?

 

[Bama Rambler]

I would try regular shocking first and see how that goes.

 

[yossarian]

OK. I shocked again tonight.

I came home from work today to a very clear pool. I still brushed some sediment off the bottom, but it was negligible compared with before. And it did not really cloud up the water.

One additional question. My FC this morning (7 am) was 21.5. This evening (7 pm), my chlorine was 9.5. My CYA is somewhere between 30 and 40 (I re-tested this evening). It was sunny and warm today. Is such a drop in FC normal?

 

[JasonLion]

Yes, that is completely normal. When FC starts high you lose more each day than if it starts are normal levels.