I have a 15x30 AG pool that was installed last year. About 11000 gallons. It has a Heyward pump and sand filter with multiport valve - it can vacuum to waste and recirculate.

About filtration media: The sand tank has zeolyte. According to label recommendations on the zeolyte, when I installed it last year, I only included about HALF the amount of recommended sand. Until now, I haven't had filtration issues, but the tank DID get shaken around a lot while I had it winterized - It even got rolled on its side some. However, it was sealed at that time.

About location of pool: pool is located partially underneath a pecan tree. Due to the nature of our yard, we just didn't have a choice here when we installed it.

Chemistry:
Ph=7.4
Alk = 125
CYA = 40-ish
FC = 3.0 (last test for CC, about 3 days ago, was at <.5)
CH = circa 380 (I have trouble reading the color change on this test)
Phosphates - my pool store tested today and indicated no phosphates

Here is the problem: The pool has been opened since mid-March. From the start, I noticed that a very fine brown-ish "dust" was settling in the crevices of the pool, particularly along the edges. In addition, during the last few weeks, it has rained 2-3 times. After raining, the bottom of the pool tends to develop green patches, and a very fine layer of what I would call "dust" tends to fall across the bottom of the pool. When the pool is in this condition, water clarity is very good, but the walls and ladder tend to start turning green.

In response to this, I always shock and brush. I also add algaecide. Chlorine levels tend to go down to about 3ppm overnight and I then maintain them there. I run the pump constantly. I also run an automated cleaner on the bottom of the pool for about 3 hours. If I brush again the next day, I can see that I am again stirring up a layer of "dust" off the bottom of the pool.

The green continues to gather in a few isolated patches on the walls overnight, and I can also see a layer of green covering various crevices in the portion of the ladder that is in the pool.

The pool is blue-cloudy - moreso after I brush and less so several hours later. I can see the bottom of the pool, and even see the walls/bottom on the opposite side of the pool, but it is still obviously cloudy. I have tried water clarifiers and organic enzymes as well as oxidizing shock. Nothing seems to help.

I haven't yet tried this, but I suspect that, if I turned off the pump overnight, all of the cloudiness in the water will disappear as the "dust" settles back on the bottom. I'll end up with clear water and a cruddy looking layer of the dust-like stuff on the bottom.

Here are the things I HAVEN'T yet tried:

1. Let it settle on the bottom and vacuum to waste
2. Try to maintain FC at 15 until it clears (I've seen this recommended on the boards here)
3. Check for filtration problems (Don't really know how to do this)

Any suggestions?