I've seen the titular comment a few times and don't understand it. How does one complete a "proper" SLAM if you already have mustard algae? I'm assuming that's what I have because its chewing through chlorine at slam levels like nobody's business. Which brings me back to SLAM says you have to pass an OCLT first. How can you with mustard algae? Help me understand because after years and years of my pool humming in crystal clear perfect balance, my current situation has me immensely frustrated and upset.
Mustard algae "complete a proper slam then go to mustard levels"
- Thread starter doncaruana
- Start date
- Jun 22, 2014
- 47,759
- Pool Size
- 17888
- Surface
- Fiberglass
- Chlorine
- Salt Water Generator
- SWG Type
- CircuPool RJ-45 Plus
Think of it this way, and our chemistry experts will slap me if I'm off the mark. 
But there are many, many types of algae which are basically organic matter. How aggressive we treat it depends on its make-up (black algae, mustard, etc). We have a SLAM FC level developed by scientists who understand what chorine-to-CYA ration is effective in the majority of those cases. At the same time, some algae has the potential to leave residual components (macrobacteria, roots, etc) that need a final push. That's why the regular SLAM FC ratio) is effective, followed by the final MA level to eradicate residual matter. Also keep in mind we consider your pool. Vinyl is more prone to fading at very high FC levels, so that's another reason we don't just run a higher MA ratio for day or weeks. It's simply too harsh on the material. @Donldson did I miss anything?
But there are many, many types of algae which are basically organic matter. How aggressive we treat it depends on its make-up (black algae, mustard, etc). We have a SLAM FC level developed by scientists who understand what chorine-to-CYA ration is effective in the majority of those cases. At the same time, some algae has the potential to leave residual components (macrobacteria, roots, etc) that need a final push. That's why the regular SLAM FC ratio) is effective, followed by the final MA level to eradicate residual matter. Also keep in mind we consider your pool. Vinyl is more prone to fading at very high FC levels, so that's another reason we don't just run a higher MA ratio for day or weeks. It's simply too harsh on the material. @Donldson did I miss anything?Mind you I'm not questioning the mustard level just wasn't really understanding how you could pass an OCLT with it (or whatever I have) in the pool anyway. I guess the residual makes sense to me at least a little.
Do I really have mustard algae? I don't know. I have seen a couple of yellow spots, but on the floor and in spots that get hit by the sun - not sure if that counts or not.
All that having been said, after I tested this morning it does indeed look like I passed the oclt last night. And with 0 CC as well...
Do I really have mustard algae? I don't know. I have seen a couple of yellow spots, but on the floor and in spots that get hit by the sun - not sure if that counts or not.
All that having been said, after I tested this morning it does indeed look like I passed the oclt last night. And with 0 CC as well...
True mustard algae reproduces with spores that are more chlorine resistant than your typical green algae. As the chlorine isn't killing and oxidizing them it isn't causing a chlorine demand, so you pass the OCLT. Then those few spores survive until the chlorine level drops enough that they can grow faster than it kills them and that's how it becomes a chronic problem that seems to clear up with a SLAM but always finds its way back.
That said, mustard algae is one of the more misdiagnosed problems. Run of the mill green algae can be very troublesome, hiding in places where it can regrow after a SLAM and causing significant FC losses to the point where it seems to grow with impunity. That's why ladders, lights, and every nook and cranny has to be brushed and get fresh chlorinated water in to it during a SLAM. Unless there's fluffy yellow stuff growing in shaded areas that poof up when brushed and it keeps happening after several fully successful SLAM Process attempts, it's probably not mustard algae.
BTW @Texas Splash I actually didn't get a notification that I was mentioned. I stumbled across this post myself and saw you mentioned me, but it doesn't show up in my notifications. Odd.
Thanks a ton for the explanation!! I've never had anything that ate through so much chlorine before and my water has remained crystal clear. So I'm flummoxed as to exactly what it is. I've never had this particular scenario so I'm doing a lot of question asking and head scratching! Thanks for the help!
- Jun 22, 2014
- 47,759
- Pool Size
- 17888
- Surface
- Fiberglass
- Chlorine
- Salt Water Generator
- SWG Type
- CircuPool RJ-45 Plus
We can't see your Poolmath test logs, so if you post a full set of test results along with a pic or two of your pool from a couple different angles, we might see something to help you crack this chlorine demand mystery. Thanks @Donldson for chiming in. Give me a thumb's up if you got this test tag. Maybe the earlier post was just odd.
Well, I've just been doing chlorine and CYA during slamming but before that pH was 7.6, TA was 100. I don't generally pay much attention to CH and haven't even tested it recently to be honest. But 2 nights ago I went from 15.5 to 4 overnight on FC, then I went from 12 at 8am to 10 at noon, when I added another gallon (which should have taken me up to 18, although I didn't test it) then down to 8.5 by 9pm. I put another gallon in and actually ran the pump for a bit, and held at 17 overnight. Here are pictures from 9pm last night and 6pm today. These pics don't do the clarity justice, so I posted the originals on imgur. The one from today is from my upper level deck, about 12 feet in the air and back about 6 feet from the water's edge (about 5.5 of water in the center). I haven't checked the levels today though. I back to woods (with branches overhanging the pool 
) so I get a lot of junk in the pool under the best of circumstances and I haven't run the dolphin the last couple of days anyway on purpose. Still crystal clear but the entire pool gets sunlight when the sun is out (partial today) and there's no yellow anywhere in the pool today. Planning on having people over tomorrow so taking a bit of a calculated risk that I'll probably have to beat the Crud out of this some more...
) so I get a lot of junk in the pool under the best of circumstances and I haven't run the dolphin the last couple of days anyway on purpose. Still crystal clear but the entire pool gets sunlight when the sun is out (partial today) and there's no yellow anywhere in the pool today. Planning on having people over tomorrow so taking a bit of a calculated risk that I'll probably have to beat the Crud out of this some more...
- Jun 22, 2014
- 47,759
- Pool Size
- 17888
- Surface
- Fiberglass
- Chlorine
- Salt Water Generator
- SWG Type
- CircuPool RJ-45 Plus
Certainly looks good. It does sound as though you could use some consistency with the testing. That could prove to be the difference. Enjoy tomorrow and be sure to check teh FC just before and after the party. Lots of swimmers generally means lots of stress on the water.