[hahnmeister]

Another very easy way to make one of these is to use a cannister filter, like an eheim, and pack it with sulphur media and crushed coral, then run the intake right into the intake so its a big loop. Then, in this loop pipe, tap in a couple 1/4" lines for inlet/outlet. Cheap, simple, and works very well. In fact, the very first reactors of this sort were done with eheim classic cannisters in this manner.

You have to watch the ORP of the output though... too high of flow, and the reactor will turn aerobic and produce nitrates. Too low of flow and the reactor will turn on itself. Because of this constant need to monitor (usually though, its set and forget) and the alkalinity problems that have come up with it, I have resorted to using my skimmer and the 'vodka' method with greater success (much easier to impliment).