Phosphate Reactors.

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Reactors for phosphate removal are fluidized reactors, just like fluidized bed sand filters.

Fluidisation will greatly increase the life and effectiveness of phosphate media (eg. Rowaphos) as it allows a larger surface area for reaction with the water and prevents channels from forming through the media.
They also work great for carbon.
Water is fed in to the reactor with a small pump or fed off return pump and adjusted so the media is suspended but not so much that it is returning to the aquarium.
They are unlike most calcium reactors where the media isn't moving in the chamber and water percolates up through it.
When the output water no longer measures lower in phosphate than the tank water it's time to replace the media.