I have been struggling with Mustard Alae all last summer and here it is again this spring. I have a 2 year old 10,000 gallon above ground and I am out of options aside from closing it this summer or taking it down completely. My fingers are crossed as I just added 4 Lbs of Cal Hypo last night. The chlorine levels were already at 15 before adding the 4 lbs with a CYA of 50 and PH of 7.4-7.6. I have to think nothing can survive this level. This stuff was growing in front of my eyes at 15ppm. I guestion if if its sand sometimes building up at the seams etc. because it comes back so fast. Today I plan to turn off the filter and see how much it grows back. I know people are not fond of pool RX but I am at the end of my rope. Any suggestions? Should super high chlorine levels kill this? Is it possible I have to drain my pool and clean the liner somehow? Any input would be greatly appreciated I am out of ideas and defeated.
Don't know what to do now.... Mustard Algae
- Thread starter jjmay77
- Start date
I just got rid of a SEVERE case of mustard algae. Here is what I learned. Forget the yellow out type of stuff. That will cost unnecessary money, waste your time, and mess your pool water chemestry up. Unfortunately there are no easy inexpensive ways to do it (because of chlorine prices), BUT ITS VERY DOABLE. Make sure your filter is good and clean first. Changing the media is best. Then try to get your PH on the low end at 7.2 because chlorine loses some of its punch the more the PH goes up. Make sure your TA, and CH are acceptable and know your CYA for obvious reasons. Go buy you 20 or 30 gallons of the Essentials 10% Chlorine at Wal Mart $100 - $150. Heres the most imortant thing: As long as you have visible mustard algae VACUME TO WASTE EVERY DAY. Trust me, this is BIG. If you are vacumming to filter you are keeping billions of live and dead algae in your system which just exasperates the problem. GET RID OF THEM. So fill your pool each night to its capacity and vacume to waste once a day. Sure you lose a little chlorine but the offset of getting that algae out is more than enough to compensate, plus the exchange of water is lowering your CYA and making your chlorine more effective. The second most important thing is BRUSH, BRUSH, BRUSH. Every day at least twice a day and more if you can. The brushing breaks them away from their clinging ways and they cant live suspended in the water with the chlorine, this is why you BACKWASH every day as needed to get those that died (in suspension) out of your filter. Mustard algae are invisibly small but think of them as having sharp claws that dig in and cling to your liner. Then think of them having a shell on their back that protects them from the chlorine while they are hunkered down. When you brush you are knocking away layers of them, but as long as there are a few left clinging they will breed. Their offspring are the "new" brownish dust you brush up every day but (DONT BRUSH THEM UP). Vacume those offspring to waste then brush the invisible clingers peeling more of them away and weakening the ones that are left. Do all these things daily while keeping your FC above mustard shock level and you will rid your pool of them. After 4 or 5 days when things look better DONT SLACK OFF. Look very closely and find those problem spots where they are still hanging on. While still brushing and keeping your FC at mustard shock level take a rag and soak it with chlorine. Wad it up and throw it in the pool pushing it down to the problem spot and putting something on it to hold it in that spot overnight. Either this or you can shake powder shock and let a small pile fall and lay on top of the problem spot. Just find some way of concentrating chlorine on your small problem areas for a day or two while brushing and keeping FC levels up. Do these things and in a week you will have no more mustard algae.
Dont drain your pool. This will ruin the liner. And dont worry about putting too much clorine in. I had my chlorine over 50ppm for a week and kept everything circulating and no harm was done. I'm not suggesting that you put over 50 ppm chlorine in your pool, I'm just saing dont freak out or worry too much about destroying everything if your FC gets up to 20 or 25 ppm for a day. Its best to operate at the suggested mustard shock levels according to your CYA but if your gets a little high for a little bit dont let that concern you too much. One other thing. I forund that the mustard algae actually grew LESS when my filter was off and MORE when it was on. That sounds backwards but it was my experience. Doesnt matter though. Your filter should remain ON and BACKWASHED reguraly 24/7 during the entire SLAM process.
Welcome to the forum! 
Reading between the lines, I suspect you may be misinterpreting some dead algae for live algae.......I may be misreading, tho.
Regardless, If you can post a current set of test results from your own good test kit, we can get a better idea of what you have. Also, an actual pic of your pool water helps enormously.
Do NOT use high levels of chlorine held down on the pool surface........that's not a good plan at all.
Reading between the lines, I suspect you may be misinterpreting some dead algae for live algae.......I may be misreading, tho.
Regardless, If you can post a current set of test results from your own good test kit, we can get a better idea of what you have. Also, an actual pic of your pool water helps enormously.
Do NOT use high levels of chlorine held down on the pool surface........that's not a good plan at all.
Thank so much to all of you for your great replies. As of right now I think things are looking better. I think the people at the pool store lead people to these products and don't have a full understanding. It seems like the high chlorine levels have stopped any new growth and I am now seeing either dead algae, sand etc. collecting at the seams. I have been vacuuming that to waste and its less every time. I was also brushing regularly. I was going to call the Men in Black next if this stuff grew at this level of chlorine. I guess now I am preparing for what is next. I have been learning on this forum and am scrapping how I have been doing things. I bought liquid chlorine and a TF-100 test kit so I can measure CYA and accurately measure free and total chlorine. If CYA is over 50 I was going to drain some water. Test kit hasn't arrived yet so I am relying on Leslie. I will not use the pool RX. Does my plan below seem good after the levels come down?
1. Get TF-100 test kit
2. Backwash filter regularly after cleanup
3. Replace water to lower CYA
4. Start using liquid chlorine as per chart (FC needed based on CYA). Thinking I keep it on the high side to avoid new algae.
5. Balance PH to 7.2 - 7.4
6. Keep fingers crossed
1. Get TF-100 test kit
2. Backwash filter regularly after cleanup
3. Replace water to lower CYA
4. Start using liquid chlorine as per chart (FC needed based on CYA). Thinking I keep it on the high side to avoid new algae.
5. Balance PH to 7.2 - 7.4
6. Keep fingers crossed
Spoke too soon its back again after coming home form work. Same spots on the seams. Could this be pollen? Its not on the walls and the chlorine is probably 30 or more. What could grow in this? I just vacuumed to waste and brushed the heck out of it. In 1-2 hours I bet it will be back. Maybe the pool rx copper is the next try?
That is a classic accumulation point for dead algae. As the flow from the pump pushes the algae across the pool floor, it piles at the ridge a seam creates.
So you really need to do a SLAM with a good kit. No quessing and know shortcuts or trying out ideas out side the SLAM.
The SLAM is a methodical way to kill all the algae in your pool and allow your filter to get the pool crystal clear. As you know, that will require the use of your good kit and your willingness to follow the procedure precisely.......pool Rx is NOT in the SLAM process
Wobblerlorri
Bronze Supporter
- Apr 16, 2019
- 2,010
- Pool Size
- 4024
- Surface
- Vinyl
- Chlorine
- Liquid Chlorine
I'm surprised no one has mentioned the Pool School article Mustard Algae. The basic idea is to do a SLAM Process then, once that's done, raise your FC to the ridiculously high level given in the article based on your CYA and keep it there for 24 hours.
I had mustard algae last year and got rid of it following this method. You can too.
I had mustard algae last year and got rid of it following this method. You can too.
Thanks again for the information. I vacuumed last night to waste and then left the filter off all night. I had zero accumulation or growth. Seems the filter may be causing the accumulation but nothing is growing. At this point if I run the filter and get the accumulation again what would be a fix for that?
- Apr 10, 2018
- 6,311
- Pool Size
- 18375
- Surface
- Plaster
- Chlorine
- Salt Water Generator
- SWG Type
- CircuPool RJ-45 Plus
Until you get your test kit, add 5 ppm of chlorine/cal-hypo daily.
Post a full set of results after testing.
Do an Overnight Chlorine Loss Test. This will confirm whether algae is present in the pool.
You'll likely need to complete the SLAM Process to eradicate the algae.
For the benefit of those helping you, complete your signature.
Good luck!
Post a full set of results after testing.
Do an Overnight Chlorine Loss Test. This will confirm whether algae is present in the pool.
You'll likely need to complete the SLAM Process to eradicate the algae.
For the benefit of those helping you, complete your signature.
Good luck!