Hello, I had some yellow discoloration in the spa and I was able to brush it off. I noticed that it has started again in the same spot and also around a seat in the pool. My guess it is mustard algae. I am a new pool maintainer and have been using chlorine tabs since that is what the pool guy was using for past 6 years that I have owned the pool. My CYA levels are probably around 200. The water is crystal clear. I usually have couple of tabs always floating around. My FC level today, tested with Taylor 2006 was 1.6ppm. Draining pool right now during summer is not advisable so I have to just wait until cooler weather. What is my best option to get rid of the algae? I did order 8 gallons of 10% liquid chlorine from Walmart which arrives tomorrow. We hardly/never use the pool. My pH was adjusted to 7.6 today. Any advise will be appreciated.
Mustard Algae
- Thread starter noobnoob
- Start date
AW139
Bronze Supporter
If you’re actually at 200 ppm or CYA, you’re pretty limited on options until you get the pool drained.
- Feb 6, 2015
- 7,814
- Pool Size
- 12300
- Surface
- Plaster
- Chlorine
- Salt Water Generator
- SWG Type
- CircuPool RJ-45 Plus
Post a full set of current test results from your K-2006.
How old are the K-2006 reagents?
FC
CC
pH
TA
CH
CYA
Water temperature
If your CYA really is around 200, your chance of success is very very low to rid yourself of algae.
Continued use of trichlor tablets will only make the issue worse.
What are your temperatures forecast to be for the next week?
Where in SoCal?
How old are the K-2006 reagents?
FC
CC
pH
TA
CH
CYA
Water temperature
If your CYA really is around 200, your chance of success is very very low to rid yourself of algae.
Continued use of trichlor tablets will only make the issue worse.
What are your temperatures forecast to be for the next week?
Where in SoCal?
I got the test yesterday so I think they should be very fresh.
I'm in Orange County. Here are the numbers from test today:
FC = 1.6
CC = 0
pH = 7.6
TA = 180 (before adjusting pH from 8 to 7.6)
CH = 1000 (Tap/Fill water CH is 400)
CYA = 200 (using diluted pool water and doubling the results)
Water Temp is unknown.
I brushed the pool in the evening and most of the stains are gone but I'm sure they will return.
I
Your SLAM level FC target is 79ppm with CYA=200.
But the algae probably isn’t mustard algae, it’s just regular algae because you have almost no chlorine and sky high CYA. You can stop using the tabs to keep it from getting worse, but there’s no good way to get rid of all that CYA without replacing the water.
if your CYA is really 200ppm, then you need to maintain FC level of 15ppm AFTER you get rid of the algae with a SLAM.
Your SLAM level FC target is 79ppm with CYA=200.
But the algae probably isn’t mustard algae, it’s just regular algae because you have almost no chlorine and sky high CYA. You can stop using the tabs to keep it from getting worse, but there’s no good way to get rid of all that CYA without replacing the water.
- Feb 6, 2015
- 7,814
- Pool Size
- 12300
- Surface
- Plaster
- Chlorine
- Salt Water Generator
- SWG Type
- CircuPool RJ-45 Plus
What is the temperature forecast for the next week or so?
Are you inland or nearer the beach in OC?
Are you inland or nearer the beach in OC?
The temp forecast is high 70's for next 10 days or so. Pretty mild for September. I'm very close to Disneyland so not at the coast nor inland.
That's a little comforting to hear that it could be regular algae. The spots are probably 2% in area compared to the rest of the pool. I will slam it to a high level.
I wish I had run into TFP before Leslies. I have a huge stock of tabs which I will use until I'm ready to drain the pool later this year or early next year. After that I will switch to liquid choline as recommended here.
- Feb 6, 2015
- 7,814
- Pool Size
- 12300
- Surface
- Plaster
- Chlorine
- Salt Water Generator
- SWG Type
- CircuPool RJ-45 Plus
Then it's not too hot to do a full drain/refill.
You can also spray water on the exposed plaster as it's draining/refilling.
If you don't already have one, rent a sump pump from Home Depot.
Check with the city to see where you need to drain the water to. Some allow draining to the street. Other require draining to the sanitary sewer via a sanitary sewer cleanout, possibly in your front yard.
As the water is draining, rinse down the sides of the pool to help get anything on the exposed surface into the water you are draining.
Once refilled, chances are you will still need to complete a SLAM Process. But it should be a short one.
Beware: The longer you use the tabs, the higher the CYA will get, which then pushes the chlorine requirement higher to avoid a swamp. You’re already knocking on the swamp zone door…
- Apr 10, 2018
- 6,339
- Pool Size
- 18375
- Surface
- Plaster
- Chlorine
- Salt Water Generator
- SWG Type
- CircuPool RJ-45 Plus
This is highly unlikely. Try testing again. Make sure you are using a 10 mL sample with the multiplier of x25.
The pool man has been using tabs forever I think. I moved in 6 years ago and he always used to puts 2 of them every week and we never had a hint of green. I have continued to do that since couple of months ago when I decided to start taking care of the pool myself. I will switch over to LC as soon as I drain the pool. Until then, I would just have to deal with the tabs and keep everything in check.
Good luck. You can usually get away with it for a couple years and sounds like you’ve done so.
I did try it with 10ml and 25 multiplier. We have very hard water in this area.
Here is update from today. Last night FC was 2ppm and I added 2 gallons of 10% LC. This morning FC level is 20.5ppm. I have brushed away the algae stains rather easily this morning. Since the water was crystal clear other than few algae discoloring, and from the advise above, I am concluding that it's not mustard algae so I'm not going through a full SLAM. I will keep the FC level elevated around 20 and monitor the algae growth or decline for next 3-4 days. If I see improvement, I will let FC get back to 3-6ppm. Again, the pool is not being used by for swimming. I just want to make sure it doesn't become a swamp which has not occurred in last 6 years. Please advise if any of my assumptions are flawed.
A couple concerns:
1. Keeping FC around 20 isn’t the SLAM process, but sounds like you know that. You might hold the algae back for a bit but once you let it get down to 3-6ppm you’ll be right back to where you started because you didn’t kill the algae and there’s so much CYA that it renders the tiny amount of chlorine you do have pretty ineffective.
2. The SLAM is done when’s the FC loss is 1ppm or less overnight and you don’t have any CC more than 0.5ppm.
You’re kinda stuck if you can’t get rid of all that CYA. But if you don’t, you’ll end up spending a lot of money trying to keep algae at bay.
Thank you for your input. I have never had algae in past 6 years and this started a month after I started taking care of the pool myself. It seems like the pool service person was controlling it somehow while using just 2 chlorine tabs a week. Maybe I'm not brushing the walls enough? Again, the water is crystal clear. I will run through the experiment for now and as soon as the weather cools down to low 70s I will look into draining the pool to lower the CYA.
Chlorine is what kills algae, brushing the walls just helps the chlorine work. Like said earlier, it can take a while for all that CYA to build up and fool you into thinking the process is working. He likely had to dump liquid chlorine in there frequently as well to keep it under control as that’s a common pool service technique.
Thank you again for your input. I will keep updating this thread until I drain the pool and lower my CYA.