The rainbow modules he was talking about do run through one another, one after the other.
I only ever heard of UV's on marine and ponds, I don't see why you need it for FW(as OBK said as well)
Unless this is a very big tank, why do you need the rainbow modules, when canisters work really well.
Eheim had a wet-dry unit, magnum350 had dual bio-wheels.
Hi MbunaGal---
Usually, unless the UGF is on a 10 gallon, you would not run airstones, but powerheads. Much more flow through the gravel. There is also reverse UGF, which is the "new" thing with UGF.