Control your nutrient input....(eg. Food), and max out youir nutritent output (skimmer, WC....etc). Also do some phosphate test over additives you add into the tank, if you do any chemical additives regularly.
It's impossible to eliminate phosphate. It exists naturally in everything, but you want to limit it as much as possible. Most food contains loads of it, some carbon leaches PO4. If you feed frozen food, I would recommend you thaw it out and rinse it with RO water before feeding. Try to offer only what they can finish in 1-2 minutes tops and remove any uneaten portion.
Having a caulerpa infested refugium also helps phosphate control effectively.
