Black Algae Question or weird dilemma?

bagd98rt

Well-known member
May 19, 2011
55
Corpus Christi, TX
I have a question about black algae and I’m looking for some help from the pros... The question is for a really good friend of mines pool so don’t pay attention to my sig... His pool is a inground 7000 gallon plaster pool with a 1hp Hayward Super Pump and and black round sand filter... I’m not to sure on the filter size or brand as all the stickers have come off with the sun... It has 1 skimmer and 3 returns with a waterfall... If anymore info is needed just let me know and I will do the best I can to help answer them... By the way the pool was built around 1995 or 1996 and could use new plaster... So anyways to my question and story...

He came by my house one day and fell in love with my pool and how crystal clear and sparkling it was and asked me how it looks so good compared to his and I told him that I use a method called the BBB method or what I call the The Trouble Free Pool Method... 😁 And how I do all my own testing to make sure it stays immaculate and I don’t buy the pucks and pool store chems that they trick him into buying... Anyways I started explaining to him what I do and what I follow and he was very intrigued and wanted to know if I could help him to change over and start using the same method to get his pool as crystal clear as mine... So to make along story shorter lol... We went to work and stopped putting in pucks and started using bleach instead I took my test kit to his house and started testing his water which by the way was not to good lol... Here were the numbers...
FC- 2.0
PH- 8.0
TA- 90
CH- 150
CYA- 0
So first things first I put in some bleach to raise the chlorine and dropped in some Stabalizer to start getting some CYA in the pool was first aiming for 30 on CYA... I didn’t mess with TA or CH at the time figuring it was good for now... Then we put in some muriatic acid to get him down to 7.5... We adjusted his pump run time to make sure that he filters the whole pool at lest 1 cycle a day and even made a few adjustments to the returns for better circulation... Well after about a week and him playing close attention to his chlorine daily making sure he put in enough everyday to keep it at the higher range for the 30 CYA everything was looking great... The pool was turning crystal clear and he was ecstatic... After a week and a half and doing the same the pool was even better looking until boom Black Algae showed its ugly face... Now I’ve been through pool school and read everything possible and even tested to make sure it wasn’t just green algae but nope it was black... So even though I understand that you don’t have to necessarily SLAM for black algae we did anyways cause he was reluctant that he wanted it gone and wanted the pretty pool back so SLAM is what we did... Scrubbing and vacuuming multiple times everyday and even running the waterfall for a few hours multiple times a day and staying persistent with the chlorine additions we finally were able to get rid of it after about a week and a half even after passing an OCLT we stayed on the SLAM and brushing/vacuuming routine for around 4 more days to make sure it was gone by the way there is no pool light or stainless steps or anything else it could grow on... we scrubbed everything... So we did it we were able to get rid of the algae and the pool looked great again...

Now fast forward a month or so and the pool still looks great the water is crystal clear and he has had his test kit and wants me to show him how to use it... So I go to his house and we start testing everything is looking better but a few additions need to be made here’s the numbers
FC- 4.5
PH- 8.0
TA- 90
CH- 150
CYA- Under 30 ?

So we pulled back out the Acid to get PH to 7.5 pulled out the Stabalizer and this time took CYA to 50 and left everything else alone we might have added a little chlorine also... So now that he knows how to test and tests his chlorine everyday he’s using his pool math and keeping chems in check boom a week later black algae is back!!!

So can someone please explain to me why and might be coincidental but after testing and balancing a week later the black algae shows up? Am I missing something? Thank You in advance for anyone that can explain this to me or help me out...
 

Texas Splash

Mod Squad
TFP Expert
LifeTime Supporter
Well, if it is Black Algae, we know it can be extremely difficult if the roots have sunk into the pool's surface. However what about copper? Any chance your friend dumped pool products in the water in the past and what you are seeing are black copper stains? The elevated pH will make it worse as well. You can test some dark areas with some dry acid if you have any. Maybe worth a shot in case it's not BA.
 

bagd98rt

Well-known member
May 19, 2011
55
Corpus Christi, TX
Well, if it is Black Algae, we know it can be extremely difficult if the roots have sunk into the pool's surface. However what about copper? Any chance your friend dumped pool products in the water in the past and what you are seeing are black copper stains? The elevated pH will make it worse as well. You can test some dark areas with some dry acid if you have any. Maybe worth a shot in case it's not BA.
Well I can say that I’m not familiar with copper stains other than what I have seen on pool school pictures but I sure can check that... Too bad the K2006C kits that we both have can’t check for copper and we can’t depend on the pool store to give us any accurate readings... But I did let him know from the very beginning to stay away from any products that contain copper like Clorox etc... what he did before switching though is something that I don’t know. As far as what he has told me that he has ever used was just pucks from Leslie’s... But is there any explanation as to why it only seems to spring up after we balance the water? Which would mean dropping the PH?
 

Texas Splash

Mod Squad
TFP Expert
LifeTime Supporter
But is there any explanation as to why it only seems to spring up after we balance the water? Which would mean dropping the PH?
Hard to tell. But along with the pH, as the FC level was increased, it could cause copper to show more. The Clorox bleach wouldn't do it, but other products with copper would like algaecides or sanitizers labeled "blue". Figured it was worth looking into along with the BA scenario.
 

bagd98rt

Well-known member
May 19, 2011
55
Corpus Christi, TX
Figured it was worth looking into along with the BA scenario.
Yeah I’m definitely going to look into the copper cause it could be that I’m guessing also... So at the time it appeared the last time I did do a couple of tests after having it slamming for a few days or more I brushed with the stainless steel brush and sprinkled some shock on the black spots and let it sit for a little while and I did notice that it got rid of a good portion of the black spots... I guess that’s what makes me think it’s BA but like I said I’m not real familiar with copper and how it reacts that’s why I came to the pros for help... So here is another little dilemma we found... It doesn’t seem like his main drain is working very well if at all... I plugged up the skimmer to test it and the pump started cavitating so we shut it off and reopened the skimmer and it went back to normal...