mustard algae, pollen, or ecoklean

[aylad]

#1, stop listening to the pool stores!

If you will measure your chlorine level at night after the sun is off the pool, and then measure it again the next morning before the sun is on the pool and compare the two, it will answer that question for you. If you've lost no chlorine overnight, then you don't have mustard algae, or anything else the chlorine needs to clean. If you've lost more than 1 ppm of chlorine overnight, then you probably have algae and need to shock the pool. But to kill mustard algae, shocking isn't going to be a one-time thing--it's going to take shocking to the right level and maintaining that level until it's dead. Take a look at the best guess chlorine chart linked in my sig for more info....

When you shocked the pool, how high did you take your chlorine level, and what is your CYA?

[PoolDoc]

Mustard algae can
+ looks like greenish or yellow powder on the surface
+ will brush away freely
+ returns within 24 hours, unless the chlorine is very high
+ tends to appear in shaded areas of the pool.
+ will never be on the floor of the pool where people step.

I have no idea what ecoklean is; pollen will be in piles or ripples, not an even film of powder.