Phosphate Reactors.

[Pescador]

I've got an old Red Sea Merlin fluidized bed that is basically the same thing. (it's now an effluent chamber on my calcium reactor)
The only difference is the Phosban has plastic grates at the top and bottom with round 1/2" coarse foam pieces to help keep the media in the reactor.
It wouldn't be hard rig it up for Rowaphos.
It doesn't take a lot of flow through the reactor, just enough until the surface starts to move.
Rowaphos also recommends flushing out the reactor with fresh water to remove the fines when using it in a reactor.