So, here is my feedback. First, filters are great for growing colonies. They put structure right where the water is flowing, allowing the bacteria to hang on to something and stay right there.
The bad thing about filters is that they trap organic matter. This concentration in one spot, if there is a lot of decaying things in the system can actually overwhelm the bacteria in that spot. Again - my opinion only - but it's better to have those organics spread more evenly throughout, giving the bacteria lots of room to make colonies and convert the organics into ammonia, then nitrite, then nitrate.
Think of it this way - drop 50 mL of ammonia into the res. It's then spread through the whole system and bacteria on every surface takes a bite. IF there is a lot, those bacteria will grow exponentially to eat as fast as they can. This happens everywhere in the system.
If you put all that in one spot (your filter) the colony has less coverage, less area to reproduce, less everything.
The only reason I see to put a filter in a RDWC system is to protect the pump(s). I've never had a pump break because of detritus in the res personally.
It's just one more thing to maintain too.
All that said, it will be fine if you want to leave them on. Especially if you don't really have much organic waste in the system. But then what do you need them for?
