I hate to be the nay sayer but... the fbf filter I built did not reduce nitrates. It did however work great as a bio filter. here is the link to the build. http://www.monsterfishkeepers.com/forums/showthread.php?195926-Fluidized-bed-in-a-wet-dry-filter
you need to use the correct media in the fbf! since placing these in line our nitrates have decreased big time!!!
also we are using deni balls in one of the fbf's with even better nitrate removal!
and peter just to clear this up JAD also do a complete nitrate filter!!! looks just like a fbf but has it own built in pump and is filled with bio balls
they say on the instalation manual that water is passed through these balls at a slow rate with no oxygen getting in the bacteria that thrive in these conditions are the nitrate removers in any system
so please re-check yourself got to JAD and ask? are they wrong!!!! are many other ray keepers that use the fbf all wrong too lol
anyway they work for us lol i dont care if they dont for you or ya not interested in them if the latter why post lmfao