Algae but FC high and steady

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WhitB08

WhitB08

Well-known member
Apr 1, 2016
146
Murfreesboro, TN
I have learned so much from this site since moving into an existing home with a pool. From the information here and the suggested taylor K 2006 test kit, I've been taking care of my own pool successfully for a year and a half.
Everything has remained balance and free chlorine high enough in correspondence with my CYA level, yet I am in the beginning stages of algae growth on the bottom of the pool. I know it's time to start the slam process, yet I am confused by the fact that the FC has remained at 6 ppm for the last 3 days since algae first appeared. Once I start the slam process, how will I know when it's time to stop if I am not having any overnight chlorine loss?
Also why would I have algae growth in the first place? The following have been my constant levels over the past few weeks leading into the algae growth and today (3 days after algae first noticed). I know I need to raise my CYA, but I plan to work on that after they slam process is complete.
FC: 6
PH: 7.7
TA: 60
CYA: about 40-48
CH: 80
 
I have two questions...

How confident are you in the accuracy of your cya test? It's very subjective and has to be performed in the right time and conditions. Although with your SWG your cya could be much higher and still not do too bad.

Hows the circulation in your pool? If algae starts growing in dead spots, it can then spread. Follow up question to that? Have you brushed and vacuumed regularly?
 
You may be correct on the CYA reading being inaccurate. I read about cya testing for quite a bit last night, and I have been holding the cylinder about chest level instead of waist level when testing. Thst may have my reading coming out a little lower on the scale than the true results. I started slam last night and bumped my FC target from 16 to 18 just in case my cya was a little higher than I thought. Do you think I should aim for FC 20 to be safe?

Circulation is pretty good, but weaker on the side of the pool furthest from the pump. This is the side the algae first appears.

We run our robotic cleaner (TigerShark) on a full cycle weekly and I brush the stairs and tanning ledge then as well.

Started slam at 9pm last night and checked hourly until 11 PM when I went to bed . I used pool math calculator, but somehow overshot and FC was a little higher than I had intended at 20 when I went to bed. FC read 17.5 at 7am this morning, so I added 18 ounces of 8.25% To get back to a FC target of 18.
 
"clear" obviously means no more green dust on the floor of the pool, but what about cloudiness after the green dust is gone? Do I wait until all cloudiness is gone or just until the green dust on the bottom disappears to consider the water "clear"?
 
WhitB08 said:
"clear" obviously means no more green dust on the floor of the pool, but what about cloudiness after the green dust is gone? Do I wait until all cloudiness is gone or just until the green dust on the bottom disappears to consider the water "clear"?
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Clear=crystal clear ;)

After SLAM, you should consider bumping CYA up to a higher level as reccomended for a SWG as I see you have one in your signature. I resisted doing so all last year and had reoccuring algae as well. This year I've bumped CYA up closer to 80 and keeping chlorine closer to 8 and having a much better year.
 
WhitB08 said:
I do plan to do that, but I'll admit that I'm scared to get it up that high in the event that I have to SLAM in the future. Thanks for the advice.
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I totally understand. I was the same but saw the error of my ways. Once water is CRYSTAL clear and I mean hunt up all cracks and crevices to brush. At that point when you'd let FC drop but it's still at SLAM level go ahead and get that CYA up before FC drops. Then let it creep down to the correct level for your new CYA and adjust SWG accordingly.
 
Living on the west coast of central Florida, mustard algae sometimes occur in small patches in corners during the very hot summer months. I have found that with regular brushing/vacuuming, along with backwashing and replacing my DE powder every 4 to 5 weeks, goes a long way in curbing these little patches of mustard algae.
 
FC of 6 for your CYA is right at the minimum of what you want to maintain. Is it possible that you are dropping below that at some point during the day?



The minimum FC/CYA ratio is .075:1 but I like to maintain .1:1 just to have a little cushion.
 

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Thanks for all the help! SLAM went well and ended after a few days. I adjusted CYA and then let chlorine drift down. I was a little worried, because we were leaving for a weeks vacation. But I returned and FC was right where it needed to be at 8 ppm and I had a nice clear pool still. I think my CYA may need to be a little higher, but I have a terrible time determining that test. I think I am at 60, but again I'm iffy on my judgment on that one.
 
WhitB08 said:
... I think my CYA may need to be a little higher, but I have a terrible time determining that test. I think I am at 60, but again I'm iffy on my judgment on that one.
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you might consider getting the cya 50 std from tftestkits next time you order something. it helped me gain some confidence in my tests, i was reading a little low compared to the standard.
 
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pookiesunshine said:
you might consider getting the cya 50 std from tftestkits next time you order something. it helped me gain some confidence in my tests, i was reading a little low compared to the standard.
Click to expand...

Well, looks like I will be ordering this. I just went out to throw in my automatic vacuum, and noticed a tiny line of green in the corner of the pool. I immediately tested and
FC: 10.5- I suppose it crept up due to the cloudiness over the last couple of days.
CC: 0
TA: 70
pH: 7.8
CYA-? I just ran out of the test reagent before getting it up to the 14 ml mark- I tried it anyway and I am at 60 with not even enough reagent. However, no stabilizer has been added in over two weeks and at last test a few days ago it was at 70.
What gives??? FC is high, no CC and yet what looks to be a tiny bit of algae has grown. Although I wasn't completely confident in my CYA testing, there's no way it could've been much higher than 70.
 
Brushing weekly, swimming often to thoroughly mix the water? Are you testing your FC at the low point of your SWCG cycle each day? Typically that is in the AM just before it turns on.

Good luck.
 
I read somewhere on the site to test FC in the early evening and that is when I typically do, however today when I noticed the green spot, I tested around 11 AM after the pump and SWG had been running for about three hours.
Brushing weekly as well as running the Tigershark. I don't think anybody's been swimming in at least 10 days or so. The kids are back in school now.
 
As long as you test at the same time of day, it is OK, but my view has always been I want to test when it is most likely my FC is the lowest. Since a SWCG adds chlorine while on, the lowest time, during a 24 hour period, would be right before it turns on for the day.
 

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