First, just want to say THANKS for all the good information out here- I have been dealing with algae in an Intex 10,000 gallon pool for the past 2 years off and on and, using a combination of ideas found here, got it to clear yesterday!Even better, I now understand the root causes and how to keep this from happening to me again- so thanks!
Here's what I did-
first, I bought a GOOD test kit ( home depot, $14.99) along with a concentrated algecide and some sink and sweep, which basically coagulates everything and makes it sink to the bottom
Next, i checked all my levels, made sure I had PLENTY of chlorine/free chlorine in the water and adjusted the alkalinity- mine was low, and that had not been showing on my little test strips. I used 20 mule team borax to bring up my alkalinity- about a half a box.
After letting my pump and filter run for about an hour, I rechecked my alkalinity level and it was fine. SO I added algecide - it was a 20% algecide from Home Depot and I put in 13 ounces which is what it said to do on the bottle. Then I let my filter and pump run for another 2 hours to circulate everything.
At this point I had a nasty yellow/brown pool and particles starting to coagulate on the top of the water like scum. So I turned off the pump to let everything settle. About 6 hours later when I checked, the water was CLEAR, with LOTS of brown sludge on the bottom.
I vacuumed this out, dumping the hose over the side onto the ground- I had read on here that the filters on these pools will not handle this kind of gunk. Then I let the pool settle overnight and vacuumed out the rest, again dumping the water from the hose over the side.I used the vacuum from OUTSIDE the pool- the less you disturb the gunk, the better off you are.
Then I replaced the 4 inches of water I had lost, adjusted my levels and added 3 ounces of algecide as a preventive. I put in a brand new filter cartridge and threw a little algecide in the filter well as well, just to be certain I'm happy to say , that after running the filter and skimmer for 4 hours, the pool is SPARKLING CLEAN and all my levels look good.
Hope this helps those of you who have above ground pools.