Best way to reduce just phosphate.

[Fennel]

Careful with dosing lanthanum chloride, your lanthanum levels will rapidly escalate and you will risk losing your SPS. Your tank looks pretty good for phosphate levels of over 0.5ppm. What types of food are you feeding?

What neutralizes lanthium? Lanthanum?

 

[AvoidTheNoid]

For what it's worth, I was struggling with the same thing and could not for the life of me figure out where it was coming from. Turns out the TDS meter reading 0 on my RODI was a lie. Every water change just added more PO4. Every time the ATO fired off, more PO4 added. Nothing more than a PSA, but it's worth checking on your end.

I ran into a similar issue with silica. My DI cartridge wasn't functioning correctly and I kept getting diatoms after water changes. I stopped assuming my DI cartridge was OK and got a TDS meter to actually measure it and saw the DI cartridge was bad. Painful mistake that could have been avoided by a ten dollar purchase