I believe either will work, but PFS might be best, and the power of the pump will be important as to how much fluidation you get (I use about 500gph into the FB to get the movement I want).
If you use play sand, you may want to make the tube quite long, because play sand is light, and grains could easily overflow the filter, get into your pump and destroy the impeller.
If you use play sand, you may want to make the tube quite long, because play sand is light, and grains could easily overflow the filter, get into your pump and destroy the impeller.
