Does the first appearance of Algae require a SLAM?

[kathy58]

Good Morning!
I am new to this process, and successfully completed our first SLAM on an 18,000 gallon in ground pool on Aug 12. It worked beautifully! I let the fc levels drop naturally, and the water is crystal clear. I maintained the pool at 11fc (we have cya of 80 and plan to reduce that with new water at the beginning of next season - only 2 more weeks left in this season for us now).
This morning I noticed a very light covering of algae on the floors and walls as I was brushing. Does this new appearance of algae require another SLAM? Can it be killed with a slightly higher level of fc or must we always go with SLAM levels?

Using the Taylor 2006 kit our readings are:
FC 11.5
CC 0
Ph 7.6
TA 80
CYA 80

Your thoughts appreciated!

 

[Jimrahbe]

Kathy,

In theory, if you had killed all the algae during the first SLAM you should not have algae now.. I suspect you killed most of it but not all..

Because the season is almost over, and you plan on new water next year, I would go with a little extra chlorine now and enjoy the pool while you can..

Thanks,

Jim R.

 

[kathy58]

Thank you! I had hoped that after a SLAM and keeping the fc levels correct for the cya I wouldn't have algae again - I am happy to hear that is the theory anyways! So happy we found this forum - next year will be amazing! Thanks again

 

[Msch99]

If not now, next year, double check ladders, light niches etc. May have some semi hidden spots that allowed some algae to remain. Maybe a difficult to brush area?

Maybe not enough to affect OCLT, but enough to allow algae to take off again.

When you get a chance, put your pool info in your signature. It helps the experts and saves you typing it every post. Settings/Signature. See other posts for examples. If on phone, need to turn sideways to see them.

Good luck!

 

[kathy58]

The algae around the ladder that may not have been brushed would not be killed in a SLAM? We passed the OCLT for 2 nights, but if it was a small amount, then perhaps that was the issue. I assumed the high fc would kill all of the algae it touched!

 

[mknauss]

I assumed the high fc would kill all of the algae it touched!

Algae is surprisingly resilient. It creates a biofilm to protect it from harm. So brushing / disturbing it breaks that biofilm and the chlorine can attack it.

That is why brushing is so important to the success of the SLAM process.

 

[youmyboyblue]

Same exact thing happened to me.. no algae all summer, then when I went out of town for a week, some well-meaning friends were going to add liquid chlorine nightly for me. Well that didn't happen as well as I'd hoped.. they even sent me pictures as the algae grew. I should have just used some trichlor pucks since my CYA is only around 25-30 and have room to spare.

When I got back, I SLAM'd for about 5 days. The water was clear, OCLT passed, 0.5 to no CC, so I let the chlorine level come down and maintained the level. But the algae came back . I plan on keeping the pool open for a few more weeks, so I went ahead and started another SLAM today. The only thing I can figure is I didn't SLAM enough last time and there was still some algae left over. That or there was algae on the solar cover or something.. I might try to scrub it this weekend. There aren't too many places for it to hide in the pool..

 

[kathy58]

I truly didn't appreciate the need to get every last spec of algae brushed. Thanks for stressing that to me now. I will be extra diligent next season. Just closed the pool today due to upcoming vacation and not wanting to ask someone to tend to it in our absence. Thanks again!