Algae spots

Mike5150

Active member
Apr 3, 2010
44
Hi there!

I'm having trouble getting rid of what I THINK are algae spots all over the bottom of my pool. I had a small outbreak of algae about a week and a half ago. By small, I mean to say that the water was tinted a cloudy green. Compared to some of my previous outbreaks, this was nothin! I kept my pool at shock level for 5-7 days (I lost count but my best guess is 6 days...no less then 5!) The water is back to being clear, but I have a bunch of little blobs of green all over the bottom of my pool. They range in size from about the size of a quarter, to no larger then the size of a baseball card. I brushed all the spots once they started showing up (which was day 4 and 5 of shocking) and they usually re-appeared in a short amount of time. On day 6 I tried vacuuming, and they didn't seem to come back so I stopped shocking. About a day later they came back. Normally I have my pool cover on except when we are swimming, but since I got the algae it's been off. I doubt this could be the cause, but I'm mentioning it just in case. Do I need to get my filter running 24/7 again and get back up to shock level, or can I get rid of this stuff if I keep vacuuming? It seemed to help out when I did it earlier.

Thanks!
 

svenpup

LifeTime Supporter
Nov 18, 2009
835
Sacramento, CA
Hello!

If you post a full set of numbers, including CYA, it will give a better idea of what is going on. Also pictures are great for diagnosing.

Are you sure you are done shocking? Have you read "How to Shock" in pool school? (link in my signature)
 

zea3

Mod Squad
TFP Expert
LifeTime Supporter
Jul 10, 2009
11,555
Houston, Texas
This may be dirt and dead algae collecting in depressions in the floor. Do they only show up after the filter has been off for a while?
 

Mike5150

Active member
Apr 3, 2010
44
Numbers! Sorry, I meant to post that in my first post.
FC-10
CC-0
TC-10
pH-7.2 (I just added borax to get it back up to the 7.6-7.8 range)
TA-90
CH-210
Cya-40-45 (Still have a hard time telling if the dots really there, or if I just WANT the dot to really be there!)

I should also note that during the whole time we were shocking, the CC's never got above .5, and most of the time that was even questionable. My Cya was a solid 45 when I started shocking, so just to be certain I used 50 in the pool calculator which gave me a shock level of 18. I kept my FC in the 18-22 range for about 6 days, there were 2 times where it dipped to 16 (which still should be fine for a 45 Cya).

I have read most of the articles in the pool school (Pool School is a perfect example of why the internet is such a great thing!!!! LOVE IT!) As for if I'm done shocking, my CC's haven't really moved the whole time, the water is clear, and the chlorine doesn't move much at all overnight.

As for the comment about dirt and dead algae, that's kinda what I was wondering. They were showing back up while I was still shocking (and running the filter 24/7), but not nearly as much as they are now. After vacuuming in the morning on day 6, they didn't show up until the next morning. I shut the filter down around 8pm on day 6, so yes they showed up in full force once the filter was off.
 

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Mike5150

Active member
Apr 3, 2010
44
Something I am also noticing is that the spots are dark green, but there are a bunch of areas that look to have a yellowish (almost sand colored) film. Could I have mustard algae?

If I do still have algae, am I remembering correctly that I should not vacuum up the spots at the bottom of the pool unless I vacuum to waste?
 

JasonLion

TFP Expert
Platinum Supporter
LifeTime Supporter
May 7, 2007
37,880
Silver Spring, MD
It is usually simplest to vacuum up the algae normally, and then backwash/clean the filter. Though in some cases vacuuming to waste might be easier.
 

Mike5150

Active member
Apr 3, 2010
44
JasonLion said:
It is usually simplest to vacuum up the algae normally, and then backwash/clean the filter. Though in some cases vacuuming to waste might be easier.
Ok, great! I thought I read somewhere that algae was smaller then most cartridge filters could handle so it was a waste of time to vacuum it. I thought I remembered a big green cloud coming through my return jets a few years ago when i tried it, but I also remember the filter was really old.
 

Mike5150

Active member
Apr 3, 2010
44
Ok, after 2 days of vacuuming (once to waste and once through the filter), the stuff is still coming back. It's more yellow then regular algae, but not as yellow as sand. My wife says if you took a box of crayola crayons, there is a yellow/green crayon and a green/yellow crayon. Our algae is pretty close to the green/yellow crayon, or basically it's a slightly yellowish shade of green. I think I'm going to try the mustard algae shock which for my Cya level is 27ppm of FC. I was also thinking of leaving the pool cover on the pool to help keep the sun from burning off the chlorine as quickly. So before I begin I have a couple questions.

1) At what point will the FC levels start causing damage to my vinyl liner and pool cover, or my pump/filter if at all?
2) When I shocked last time my CC level never really spiked above .5 and my water was pretty clear for the last 2 days of shocking. How long should I plan on holding 27ppm of FC to be sure that if it is mustard algae I killed it off?

Thanks again everyone!
 

frustratedpoolmom

TFP Expert
LifeTime Supporter
In The Industry
May 20, 2007
12,223
SWSuburban Chicago, IL
Shock to normal levels until the FC holds overnight. True Mustard Algae will dissappear at that point, only to return when the FC drops to "normal". So if you shock and the stuff dissappears, then raise it up to MA shock levels for 24 hours, treating pool toys, floats etc so they don't reintroduce it. Wash suits and towels in hot soapy water.

If you raise it up to shock level, and it holds overnight and you still see this stuff, then it's not algae its prob just dust or pollen.