About 2 weeks ago I purchased the intex 15'x48" metal frame pool (~4500 gal). Filled it up with well water, initially no issues, water was crystal clear. Three days later, I saw what I thought was algae on the surface of the water (realized later it was just pollen/plant fibers), and started to add chemicals to the still crystal clear water. Since my ph was low, I started with ph plus (baking soda) to ensure maximum chlorine effectiveness. I added about 1.5 pounds in front of the filter pump outlet. Almost immediately, the water turned the color and clarity of diluted milk (and has stayed that way since). That night I also added a dose of powdered shock. I also started putting in trichlor (not ideal, I know, but I already bought a bucket of it). Subsequently, I added 3.5 pounds more of the baking soda, and the ph has been ok ever since.
Though offputting, I didn't let the ugly water discourage me. Since the chlorine and ph were good, and there was no chloramine smell, I've been going in the pool with no skin reactions to speak of at all. So whatever the stuff in the water is, it's inert.
If the pool is unused for a few days, the water actually clears up a good deal, with a very fine white powder settling on the bottom of the pool. But, the slightest touch sends it into the water again. Also, in my fiddling around, this powder goes right through the filter.
At this point I'm guessing that either my well water was already very saturated with carbonate, and the baking soda is unable to dissolve; or, the cheap chemicals I used were cut with chalk or something similarly insoluble. I really, really doubt that this is dead algae.
I've been debating buying a sand filter with a much larger pump, but from what I've read they don't really filter the extremely fine stuff. Besides, apart from the white powder, I'm happy with the cleanliness of the pool.
I thought as a last resort I might try better cartridges. I found that many forum members are very happy with the unicel c-4607. However, I've also seen references to a "dotty" walmart cartridge that is even finer (Above ground bestway/intex pool problem with small particles [Archive] - Trouble Free Pool). For the life of me I can't find any pictures or links to this cartridge, and I can't find it on walmart's site either. Or, maybe there's an even finer Intex A/C cartridge available?
Sorry for the novel, and thanks for any advice at all.