Algae problem

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beechjetdriver

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Jul 17, 2011
47
Canton, MI
I'm having an algae problem...again. I had a problem about a month ago with fine green algae covering only the floor of the pool. I shocked for a few days until I passed the OCLT, and had less than 0.5 CC. I wasn't sure if it was mustard algae, so after shocking was complete I brought the pool up to mustard algae shock level for my CYA. I also put everything that touches the pool (toys, ladder, etc) into the water while it was at mustard algae shock level. After that the pool looked fantastic until today when I returned home from a work 3.5 day trip. Before I left on the trip I brought the FC level up to 12.5 and covered it with a blue solar cover. While I was gone we did get some severe storms and the air temperature got to around 96 (very warm for this time of year). When I took the solar cover off today the bottom was covered with the fine green algae again! I brushed the entire bottom of the pool and have started the shocking process. When I brushed the bottom the water turned a slight green for a bit, now it just looks very dull. I have been religious about keeping the FC at or slightly above the normal range since last month. I'm at a loss of what to do other than shock and go back to mustard algae shock level. I'm confused on how the pool can turn green with algae when I've kept the FC level within the normal range for my CYA level. What's even more frustrating is I have 2 separate neighbors that have pools, and their pools have been blue all year long using nothing but pucks in a floater :grrrr: Here's my test results from today (before I shocked)

FC-8
CC-0
TC-8
PH-7.5
TA-110
CH-170
CYA-50
Temp-78
 
Well that's the confusing part as I see it. Algae should consume chlorine, with or without the sun. Much faster than 1ppm/day. It doesn't seem to have done that.

You have 0 CC. Maybe you should perform an OCLT tonight at shock level. If it doesn't loose chlorine overnight... well that just makes it more confusing.
 
That's what I'm doing tonight. I just tested the FC level a minute ago and it was still at 19.5 for the night (shock level is 17). CC was 0.5 (hard to tell under a light bulb vs natural light). Can leaving the solar cover on your pool for an extended period of time turn it green? The solar cover has only been off of the pool for maybe 10 hrs over the past 2-3 weeks. Does chlorine need a certain amount of sunlight to "activate" to kill algae? The only other things I can think of are mustard algae that is coming back as FC falls below shock level, or my CYA test is off somehow. I've tested the CYA numerous times exactly as the TF-100 directs, and the black dot consistently disappears somewhere between the 50 and 60 mark depending on the lighting outside. Not sure about the mustard algae theory because it seems to be growing all over the pool bottom, not just in shaded areas (granted it's been covered so it's all shaded). I run the filter for 12 hrs/day. It's a 17,500 gallon pool with a 1.5 hp pump, only one return. The return is angled halfway up the wall so it's getting descent circulation. I guess I'll wait and see what happens tomorrow morning with the OCLT. Thanks for all your help!!
 
Is your vinyl a blue color? If so, then yellow/mustard algae can look green (yellow+blue = green). That would be consistent with the algae growing more when the cover was on since it prefers shade and it is more resistant to chlorine requiring an FC that is around 15% of the CYA level to control its growth though in your case even that was not enough. It's unlikely to be pollen since the cover was on (unless it was there before the cover was put on and settled). It is odd that the chlorine level wasn't consumed more quickly if there was that much algae.

One return for a 17,500 gallon pool is not very good (is this a round pool and if so what are the dimensions?). If the return were near the surface in a round pool, I'd suggest pointing it diagonally downward for better bottom circulation but for a mid-height return I'm not sure what would work well. I wonder if this is a case where The Circulator would be appropriate. I also assume that there is just one skimmer and no floor drain (since this is an above-ground pool).

Are your neighbor's pools similar to yours -- reasonably large with only one return?
 
Hi chem geek. The vinyl liner is blue, and it's 28ft round. The FC didn't drop at all overnight so I passed the OCLT, however, there was still a couple dirt looking spots with a bit of a green halo on the bottom of the pool (not many though). I brushed them and put the solar cover on just for the morning to retain some heat (only 55 air temp this morning, supposed to warm to 80). The return is pointing diagonally downward, and it is close to the surface with only one skimmer (no floor drain). Both my neighbors pools are smaller than mine with one return/skimmer and both of their returns seem to be close to the surface too. When their pump is running you can see ripples on the water surface. When mine running you can't see ripples on the surface unless it's windy. Maybe it's a case of poor bottom circulation in my pool. I'm going to continue the shock process today even though I passed the OCLT. The dirt patches with green halo's tell me there's still something living at the bottom. Should i go back up to mustard algae shock level? Also, any reviews on "the circulator"?
 

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As a follow up....maybe I've been aiming my return jet too far down. Both my neighbors return jet create a ripple in the water. Mine never has. My return is near the surface. Should I direct it more upward than downward to create a small ripple (no aeration) on the top level of water? Forgive me for my stupidity, this is my 3rd year running the pool (none have been that successful), and I never received any proper instruction on how to aim the return jet. I've only been doing the BBB method for 2 months, but It's been great up until this last algae battle. Since my chemicals seem to be balaned fairly well, I'm thinking it may be bad circulation from a poorly aimed jet.
 
beechjetdriver said:
Should I direct it more upward than downward to create a small ripple (no aeration) on the top level of water?
Click to expand...
What shape is your pool? I would keep it pointing somewhat downward and to the side (away from the skimmer so it creates a flow around the long route to the skimmer). The surface will still get stirred and the water deep down needs to be moved.
 
Round, one return/one skimmer. It is pointed away from the skimmer. I guess "more upward than downward" was a poor choice of words. I should have said pointed slightly downward, but not so far downward that it doesn't create a ripple on the surface. Is that a more accurate description of how it should be aimed?
 
If what you have is yellow/mustard algae and you don't get completely rid of it, then there are other options for you at extra cost. The two that are recommended on this forum are the use of 50 ppm Borates and using Polyquat algaecide (one or the other; you usually don't need both). Ones not recommended (mostly due to their side effects or cost, not because they don't at least partially work) are bromide/bromine algaecide, ammonium algaecide, phosphate removers, copper ion algaecides.
 
Thanks chem geek. I finished the shock process yesterday and the pool looks great. I've allowed the FC to drop to 13 since i've completed shocking, and it should be down to 8 by the end of today (within the normal range). I have realized that the algae was probably from the top of the solar cover itself. The only times I've gotten algae this year and last year is when I used the cover. I hadn't cleaned the cover in 2 years, so yesterday I bleached the entire top of the cover. The bottom of the cover was sanitized overnight when I installed it on the pool at shock level. Hopefully this will solve my problem.
 
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