PO4X4 is a novel phosphate removing resin which at first glance may seem like granular ferric oxide (GFO), but the similarities end with the color of the media. The shape and size of PO4X4 is like tiny little beads about one mm or less in diameter; the small spheres of PO4X4 is about the best design for being to fluidize this media, and keeping it fluidized even in lower flowrates.

Not only is PO4X4 supposed to remove considerably more phosphate than the same volume of GFO, the phosphate removing resin can be regenerated using a regeneration buffer which is sold separately. PO4X4 regeneration buffer is pretty caustic stuff so it needs to be handled carefully, and the media needs to be thoroughly rinsed between five and ten times with phosphate free water after regeneration.

We’re just beginning to put PO4X4 through the testing phase on a couple of systems (courtesy of Aquarium Specialty). We haven’t yet tested regeneration process and can’t comment on how much of effort is involved, but in the meantime we wanted to share these observation about a different way to keep the nutrients and especially the phosphate especially low in your reef aquarium water.