Is this a reef tank? If so, that level is way to high. You want to see less than 0.03 PO4
in your tank. Above that level it can inhibit coral growth. It can also cause excess nuisance algae growth in your display tank.
It can be brought down by efficient skimming, growing macro algae, and by using Granulated Ferric Oxide in a reactor.
BRS sells a nice easy reactor setup, and also sells some very high quality GFO
. I use them both myself to keep my PO4
under control - combined with skimming and macro algae growth. My PO4
was around 0.11. It has dropped to 0-0.02 since I started running high capacity GFO