My 3" N. Wenn spends most of his time in his borrow, most of it watching me when I'm at my desk. He ventures out once ina while but never for very long. He seems happy for now living in my elicpse 3.
I was concerned about water quality too. My solution was to plumb it in with the main system.
I ran 1/4" air tubing from the display over and down to the eclipse, I drilled a bulkhead and then ran a 1/2" PVC pipe back to the sump. Since the the feed is only fed by a syphon(drop about 20") and goes through about 25ft of 1/4" tubing the flow is just a slight stream but its enough to keep the 2 systems in the same.