Mustard Algae - Just the Basics

Hello,

I have spent over an hour on this forum trying to figure out how to eliminate my mustard algae and don't have a clear answer. I am looking for some basic answers.

Symptoms -

Brownish green material forming on certain vertical areas of my Pebble Tec pool. Around steps, lights, and also on my pool vac and hose. It easily brushes away like dust and reforms in the same spots a few days later. Have had this for about 1 year. Has not gotten worse but is persistant.

Pool Chemistry -

SWG
21,000 gal
Cartridge filters
Pebble Tec finish
pH 8
FC 2
CYA 30
Salt 3000
Temp 68 Deg F

Leslie's recommends Yellowout. This forum seems to say not to use.

Questions -

1. If I wish to shock and kill the algae using bleach what FC level must I reach?

2. How long must I keep it there?

3. How do you measure a FC level greater than 5 if the kit I have only goes up to 5 ppm?

Thanks for the replys.

Had that stuff a couple years ago and a similar CYA reading and similar symptoms. Never totally eliminating it. Kept the FC up around 15 and sometimes higher for about a week and that finally got rid of it. Measure FC a couple times a day if you can and keep the level up. You can use distilled or non-chlorinated water to dilute the sample before measuring. Diluting 1:1, double the FC reading. 2:1 triple, 3:1 X4 etc. If you can hold an FC level overnight (no sunlight) then you have killed the stuff off. Then go a couple more days.
Someone else will probably chime in with more advice.
Al

Whereas the normal shock level of an FC that is around 40% of the CYA level works well for normal green algae, it takes an FC of around 60% of the CYA level to more quickly kill (for shocking) yellow/mustard algae. So for your 30 ppm CYA, that's an FC of around 18 ppm, so not far from what Al suggested.

You need to keep that level up for an extended time such as the week Al suggested and you need to put in any poles or other equipment, floats, etc. you sometimes put into the pool. You may also need to check behind light niches and remove handrails (if removable) or any other areas where there may be water that doesn't circulate well.

This all assumes you actually have yellow/mustard algae and not just dirt or pollen. If it tends to grow on the shady side of the pool, it is more likely to be yellow/mustard algae. Dirt feels gritty, pollen feels mushy, and algae usually feels slimy.

As for a chlorine test, you can use the dilution method Al suggested, but for even more accuracy you can use a FAS-DPD chlorine test. You can get such a test here (the full TF100 kit is somewhat similar to Ben's kit and also related to the Taylor K-2006 and uses Taylor reagents).

Richard

You can also get the FAS-DPD kit at the pool store or at other places online--the TF kit is not the only one that will do the trick..

Janet

The Taylor K-1515-A is such a FAS-DPD kit, but I haven't seen it in stores. The tftestkits.com FAS-DPD chlorine kit (that is, only the chlorine kit, not the full kit) is about the same price yet has 36% more volume of reagents.

For a full test kit that also includes the FAS-DPD chlorine test for Free Chlorine (FC) and Combined Chlorine, and also tests pH, Total Alkalinity (TA), Calcium Hardness (CH) and Cyanuric Acid (CYA), there is the Taylor K-2006 kit at a good online price, though the TF100 has 36% more volume of reagents so is slightly lower priced "per test" (kit contents are described here). If you can find the Taylor K-2006 kit locally, then you'd save on shipping, though usually you can only find the K-2005 which has a standard DPD chlorine test, not the K-2006 with FAS-DPD.

Richard