Is this Mustard Algae?

[bkkari]

Hello,
We've had our inground pool for three years now and havent ever had any problems with it until this year.
It first started out after the 4th of July where we noticed our pool started to get a little cloudy and we kept losing our chlorine levels. We have 20x44 inground pool with a SWG. We kept "boosting" our SWG, but the within a day or two our chlorine levels were almost zero. Our combined chlorine then started to raise from 0 to .5, so we knew we needed to shock it and assumed we had some form of aglae brewing. We followed the guidlines on this site for "slamming our pool" and everything seemed fine for a week or so. Then we started noticing our chlorine levels again we not holding and kept slipping down again. Our pool remained crystal clear, but we also noticed what we thought was sand on our seems in the bottom of the pool and also on one of our steps. It looked beige in color (like sand), but then was not gritty like sand. Instead it dissolved when we went to sweep it or whipe it up. After doing some reading, we have been treating this like Mustard Algae. Our CYA was 60, so we have been shocking our pool with bleach and getting the FC level to the recommended 36 ppm level. We have been leaving out pool cover open as much as possible to help air it out. The FC has dropped during the day sometimes to around 26 or 27ppm, so we have raised it up again to 36 or a little higher at night. Since doing so, a few days we're no longer seeing the beige substance, but now have seen a black substance in the same areas where the beige was. Is this dead algae? ( I thought it would be white or gray, but this is has been black). Also yesterday we didnt have any residue and we thought we were almost at the tail end shocking this, but now this morning there's a little bit of black residue again, and our cc has raised again to 1.0. Of note: my husband did take out the filter last night to clean it, do you think that has anything to do with it? We started the shocking 5 days ago. Just wondering if were doing the right thing still. Any advice is highly appreciated. Also is it ok if we leave the pool cover on during the day? (and do we need to be concerned about our automatic pool cover having this algae?).

Thanks so much again for you help/advice.

 

[ping]

Welcome to TFP!

It looks like you have done some good research here at TFP but we need some basics first. Please post all test results and which test kit you are using.

Hard to say if it is mustard algae, but it does not seem like it is. To kill mustard algae you go through the SLAM process until it is complete and then you raise the FC to mustard algae levels for 24 hours and then let the FC drop to normal range. You are risking damaging the vinyl liner by keeping the FC at mustard levels for extended periods of time.

Did you pass all three requirements of the SLAM process the first time you SLAMmed the pool?

How low did the FC get since the SLAM?

The cover might have algae, light niches, ladders, etc could still be holding algae.

 

[bkkari]

Hello,
We're using TK100 test kit ( Taylor).
Our results before slamming were
FC 1.5
TC 1.8
CC .3
PH 7.4
CH 270
TA 180
CYA 60

Our pool was clear from the start. From sun-wed we hit FC ranging from 40 ( we overshot at first) to drop to 24 during daylight with pool cover open all sunny days. The sand color changed to a black color residue for one night , then gone the next day with no residue. Now back again with a little black residue ( all within same spots of where the initial sand like substance laid ( on a few seams at bottom of pool).CC ranged from 0 to .5 and now today 1.0. The OCLT was at 2ppm from tues to wed morning. During this process we have also brushed our pool walls, steps, floors 2x/day, as well as vacuumed and cleaned the filter. We have soaked and cleaned all our pool toys etc..


We're puzzled on what to do Next? For some reason I was under the impression we had to keep the FC at the mustard high algae level (36) consistently until we no longer saw any kind of residue on the pool floor, as well as pass the OCLT and a less than .5 CC. Am I wrong?... Can dead mustard algae present as black? What do you suggest? I know you mentioned harming our pool liner and equipment, which concerns me. Should we stop this process and
Let our FC drift down to normal levels again and then start over?? Please help!
Thanks again for this forum. So appreciate your expertise.

 

[ping]

Mustard algae will not be black and it grows on the walls in the shaded part of the pool, so I would say it is not mustard algae. Mustard algae will go away at SLAM levels but return when the FC drops to normal ranges.

Continue the SLAM until the pool passes the requirements:
Clear
OCLT is 1 or less
CC is .5 or less

The FC was too low for the CYA level and algae might have started to grow again, Chlorine CYA Chart

You might have passed the tests already but are dealing with the black substance which we need to figure out what it is. Run an OCLT tonight and post the results tomorrow. Can you feel what the black substance texture is?

 

[bkkari]

Ok, we passed the OCLT this morning! However our CC is still 1.0 ( per our test kit).
The small black residue is back again this am. I tried to wipe it up with a cloth but it just disintegrated when I went over it and it didn't leave a mark on the cloth. It does not look gritty, but sort of like small oil drops?..
Also a few questions: I'm wondering how I could be below the Shock FC level when the lowest we let it drop was 24? My understanding is that 24 is the FC shock/slam level.
Another question: we have not been testing our other labs since we started because I assumed that since the pH and TA mat be in accurate I'm assumed our CYA would be too. Should I still be testing our CYA daily and adjust the FC base don that daily value while slamming? We have based it on our cya level taken just before starting the slamming process on that same day. We did test our cya today just to see what level it is now, today based on our kit it showed it as being 40.
Am I best to now go with this value or the original one of 60?
I'm assuming since I still have a CC of 1.0 that I still need to continue the slamming process. On one of your previous responses you mentioned that you weren't sure it was mustard algae. So I'm wondering when I done with the slamming, should I still go ahead with reaching the FC for mustard algae for 24 hours, or should I just let the FC drift down? And if so, again whhich cya value should I use for this?

Sorry for all of the questions. Thank you again for your help.

 

[ping]

Continue the SLAM due to CC>.5 and black residue remaining. Hopefully someone else will chime in on the black substance.

I thought you finished the SLAM and the FC dropped to 1.5 before starting another SLAM. How long have you kept the pool at continuous SLAM levels? A FC level of 24 is the correct SLAM level for a CYA level of 60 and that is what I would use until the SLAM is complete. There is no need to test the CYA again until you are finished with the SLAM and want to get a baseline of the water after the SLAM.

The only test affected by FC>10 is the pH. The other tests will be accurate with the high FC level. We like to see all test results just to make sure there isn't something that is off with the balance of the water.

I would not raise the FC to mustard level once the SLAM is complete.

 

[bkkari]

Hello, so last night our FC was 25 before we went to bed. We have cont to leave the pool cover open and this morning our FC was 22. We tested it an 1.5 hours later than we normally had ( tested at 8am instead of 6:30am), but it has been cloudy and overcast. Just wondering if this would've played a role in the OCLT? Especially since yesterday we didn't see a drop. Also today the CC remains at 1.0 . The water continues to look clear and today there is no black residue. I'm wondering if it would be worth while to have our water tested by the local pool store just to see if their CC is reading differently than ours? Also my because we haven't been able to use our pool for this last week, we're concerned about keeping these high chlorine levels in the pool for extended time and certainly don't want to ruin our vinyl liner and pool equipment ( not to mention the frustration of not being able to use the pool). Wondering if it's worth while to let our chlorine levels drift down now in order to allow us to swim for the last few weeks of summer ( and give the pool liner / equipment relief of high chlorine exposure), and then readdress this issue when we're getting closer to closing the pool for season? Or in delaying this process, are we asking for more trouble? ( what if we cont to sweep, vacuum and keep chlorine at appropriate levels to try and keep this at bay until the end of the season)?

 

[Abigail K]

Cloudy and overcast or testing later does not have much bearing on the OCLT since you lost 3ppm of FC.

Don't bother with pool store testing, it would confuse you. Trust your own testing.

Our FC levels may seem high but CYA binds to FC and buffers how harsh it actually is.
We say it is safe to swim up to SLAM levels provided you can see the bottom.

 

[tschutz1]

Does your residue look like this?

I've struggled with this all summer. I'm convinced it's pollen or something. I can clean the whole pool and it seems like the pump just blows it back into the pool.


Sent from my iPhone using Tapatalk

 

[bkkari]

No, it does not look quite like that. I tried to attach a photo, but for some reason it didnt work.
Mine looked like a row of sand along the seams in the bottom of our pool. It was in a line formation in areas of the pool with crevaces. It initially was sand/taupe like colored. Then during slamming process, it was dark brown/black in color.

The last few days we have not had any residue and we've passed the overnight chlorine loss test, as well as the CC level being .5 or less. So im keeping my fingers crossed that were done....

Good luck. I'll keep trying to send a picture if i can.


ADDENDUM: I guess the picture worked after all. This picture was taken near the end of our days with this problem, so there wasnt a lot of residue left at this time. In the beginning (when it was sand/taupe like colored) there was more substance along the seams, but in the same format as this.