The second pump you are thinking about is probably a dosing pump to dose a carbon source (like ethanol) to the denitrator.. I don't think those are necessary though. you can use a syringe.
For a typical DYI coil model, you just need one pump... super slow flow... creates the anerobic environment for the bacteria... just about any air tight container would work.
I was going to try and build one out of a phosban reactor and some dead LR rubble on my 55, but I tried using AZNO3 first and didn't need to.
http://saltaquarium.about.com/cs/nit...a/aa092702.htm