How do I reduce High Phosphates & Alkalinity?

[ccnoriz1]

I just need to know what chemicals I can purchase to reduce the Phosphates and Alkalinity in my play pool
We drained and refilled the pool about a month ago. Just bought new filters. Going broke!!! need least cost effective treatment. Just before the purchase of new filters within two weeks or so the pool turned green with algae. We shocked it put chlorine tabs and stabalizer and have been running it for 2 days.

Pool store summary on water test is
Free Avail Chlorine ok 3ppm
Total Avail Chlorine ok 3
Calcium Hardness ok 250
Total Alkalinity HIGH 150ppmPH ok 7.4
Copper Ok 0
Iron ok 0
Total dissolved solids ok 1000
Phosphates HIGH 200

Pool is underground
approx 10000 gallons
filtered pump
pebble

[chem geek]

Forget the phosphates. Just maintain the appropriate Free Chlorine (FC) level for your Cyanuric Acid (CYA) level (which you did not list -- how much stabilizer was added?). See the Pool School to learn more including how to lower your TA though I'd get your pool clear first. You should also get your own good test kit -- either the Taylor K-2006 or the TFTestkits TF-100 with the latter having more volume of reagents you use the most.