needing help with Phos!

[The Guy]

Originally Posted by MitchM

It's one thing to treat the symptoms, another thing to fix the cause.
Knowing more about your set up would help, and a picture would be best.

I agree no point in trying to band aid fix a phosphate problem until you know the cause. I had high levels in my 90g and was advised to get rid of some of my sand bed depth as I had 2-3", so I removed a 5g pail and a half of real dirty sand bed and am now at 1" max. The detris build up was causing some of my problems, as well I added another wp25 wavemaker power head to increase the flow in and around the live rock which helps to blow any build up off them.
I have about 100 gallons of water volume between the DT and the sump after taking into account rock displacement. and do 25% RO water changes every 2 weeks. I also run GFO which I plan on changing every 4 weeks, until my level is at an acceptable reading, once it's there I'll check the PO4 level every couple of weeks and when I see the levels climbing I'll know it's time for a GFO change. I was using a color chart PO4 tester but find the Hanna checker is the most accurate for phosphates and use Salifert kits for everything else.
This is what I did for my system and it seems to be working for me so far, hope this helps