Need Help with High Phosphates

[LeanneP]

I haveI been having water quality issues for awhile and I have finally got an R/O water system now. I have an 86 gallon tank with a hammer coral, frogspawn and a candy cane coral. They have not been doing well and I now have a reading of 1.0 for phosphates.
Other parameters are:
PH-8.1
KH-8
Ca-390
Mg-1300
NH4, Nitrite and Nitrates all 0
I just did a 23 gallon water change a few days ago and plan to do another 15 gallons on Tues. or should I do another big one again.
I strain all my frozen food to reduce phophates. I am sure that this is from the water I was using as my cartridge filter did not seem to be doing the trick lately because our water is so bad here.
In the short term I was wondering if any one has used the phosphate removers to get my number down and how safe they are or is there a better way of getting the numbers down so I don't lose my corals.
Leanne P