Is it reasonable to expect zero algae?

[mcaswell]

The water is crystal clear, but very 3-4 days recently I'm noticing a light accumulation of what appears to be greenish algae on the walls of the pool, which is easily "dusted" off with the brush. I had been testing with strips (which led me to believe my FC level was about 4), but the TF100 drop test gave me a higher result... here's the results of the tests I did this morning:

PH: 7.4
FC: 7.5
CC: 0
CYA: 65 (I think)
ALK: 110

My FC level was actually 9 a day or two ago, so I turned down the SWCG to let the level drift down towards the recommended level on the chart (4-5).

Anyway, my question is this... if the water is clear, but I'm seeing a little algae on the walls, does this mean I should keep the FC a bit higher, or is a small amount of algae growth considered acceptable? Also, my PH was about 8.2, which I reduced yesterday with the addition of acid... could that have played a role in the appearance of algae?

--Michael

 

[Bama Rambler]

If you keep your FC in the recommended range all the time you should never see algae. You can have areas of poor circulation where the FC is lower than in the rest of the pool and that can cause problems but it's rare that's it's bad enough to cause constant issues.

With an swcg your FC should be plenty high. I suggest turning off the swcg one evening and running an OCLT. You may need to shock the pool and start from clean & clear.

 

[mcaswell]

Thanks... sorry, forgot to mention, I did do the OCLT. Yesterday evening FC was 8, and was 7.5 this morning (pump was off all night).

--Michael

 

[PSW]

Did you run the pump in the morning before re-testing water? If you do shut your pump off at night, it is suggested that you run it for a little while before taking sample in the morning.

 

[mcaswell]

I did let it run for about a half hour (with no SWCG)... is that enough time?

--Michael

 

[PSW]

I did let it run for about a half hour (with no SWCG)... is that enough time?

Yes, that should be enough time.

 

[Lershac]

I had a dead spot in a corner of my tanning shelf that did the same thing. I adjusted a return a bit and all good now. I was freaked out, cuz I run my fc a bit high and it was totally unexpected.

 

[mynewpool]

I had this same issue and it was an algae buildup. Took me a few days to clear it up and pass the OCLT, which I see you already did, and have been keeping it at the correct FC level. Since then no issues.

 

[mcaswell]

There's also a possibility that my CYA is higher than I think the test indicated... I repeated it several times, and I think I got it right, but maybe not.

--Michael

 

[brg88tx]

i have a few black algae dots no matter how high i try to keep the chlorine. i just brush them off every time i go swimming.