Most of my DIY ca rxtors I build have the flow going up, but the ca media is not fluidized due to the density (crushed shell/coral, or mined aragonite) and low flow rate.
IMHO, there is relatively little advantage to fluidize the media. The amount of media surface area is over-optimized anyway, and unless you want to make a ca rxtor with reaction chamber about the size of a ball point pen, the amount of energy in getting the flow up (bigger pump, more electricty) or less dense media (specialized puffy ca. carb. that going to cost you more) is just not worth it.
It is kewl to watch BTW, but I will use 10 Bic pen barrels instead of fluidize the media.