Algae Growth Question

[Daltex]

I have the TF-100 for a month or so but prior to getting it had been shocking my pool when I let the FC drop to low and algae started to bloom.

After reading this forum I used the calc. to estimate the shock and was successful at getting rid of the algae bloom. I got my test kit and found out that I was about at mustard shock level so since I met the three conditions to stop the slam I did.

Using the TF-100 I got everything in line chemistry wise and kept the FC at the upper goal 80% and let it drop to close to the lower limit but never below it a few times.

Last few weeks I have noticed that the walls are getting regrowth of algae now even with the FC at the upper limit and even a few ppm above it in case my CYA reading was off.

Question: Can algae regrow that fast at the upper limit if you have some residual algae to "seed" it?

I was laxed in removing 100% of the algae since I figured it was all dead anyway at the sustained mustard shock level for so long.

Is the only cure to get it back up to SLAM level and remove light niches etc.? (BTW I think that my pool sweep and attached hoses are also culprits that I don't hear mentioned often)

Pool looks great and I just want to stop my pre TFP once a week shock treatments I used to do.

Thanks in advance!!

 

[Abigail K]

The thing that jumps out at me is your use of the word "shock".
Likely you have been using dichlor/trichlor. Dichlor/trichlor contain CYA and chlorine, the chlorine is used up but the CYA remains.

Have you re-tested your CYA level? Minimum FC levels are based on CYA levels, likely you have not been maintaining the appropriate FC for your CYA. See the chlorine/CYA chart.

The cure is 1) stop using shock 2) use bleach/liquid chlorine to SLAM your pool, remove light niches etc, pool vac hose should be scrubbed down.
You need to SLAM your pool to completion.

 

[mrcarcrazy]

As Abilgail has pointed out Your use of the term shock has me a bit confused/concerned as well.

a solid trick is to leave the hoses etc in the pool when you're SLAMing. It will expose all of that to high FC levels.

If you passed the tests to stop SLAM before, then you must have allowed the pool to drop below the "min" for your CYA level. I too find it difficult to see the CYA level as a certainty, so I aim high. less harm to be done this way. if it's between 30 and 40, I call it 40... Of course I have issues seeing the color differences on the pH test as well. I just aim for "somewhere in the middle". Gotta do what ya gotta do. I'm blind so I go for "least harm" approach.

If you are using anything other than liquid bleach to chlorinate/"shock"/SLAM. then you have most likely added CYA.

If you see Algae, it's time to stock up on bleach, and get to SLAMing again.

 

[Daltex]

Sorry for the confusion over the use of the term shock. It's the level of FC that is higher then the regular maintenance level required per the:
troublefreepool.com/calc.

I'm just using the terms that are used on there. There is no mention of di/trichlor regarding shocking and I have been using bleach for over a year now.

Current CYA level is 55 +/- so I just go with 60 to be safe.

Mrcarcrazy- I did leave the hoses in when SLAMing before and I am 100% certain that the FC level didn't get below the min for my CYA level. I guess I'm just thinking that since I didn't scrub the light niches and the pool sweep hoses could this have caused algae to return to noticeable levels to the point I can see it on the walls?

Regardless I will be re SLAMing it as soon as I get a chance to be home for the duration. I travel a lot and will need to make sure I'm home for a while to knock it out. Just not really happy that I didn't do it right the first time.