Our tap water quality is pretty good apart from the added chloramines and chlorine. I've tested the TDS and it's below 200 every time.
Is there a specific need to run it through a filter? I was always under the impression that the only reason I would need to use something like a 2-stage carbon filter or higher stage RO unit was if my water quality was low or pH swings are large after aging. My understanding was that as long as my pH is stable and TDS is low it should be safe and that domestically bred discus can be kept in pH of 7.6-7.8 without harm.