It's almost odd that on this and other forums there are those that believe that even high nitrates of 100ppm+ are nothing to worry about. I am convinced that over time, high nitrates are lethal. And since fresh water in nature does not have nitrates (or levels are too low to measure) all the more reson to get them out of our aquariums.
To be honest I really developed the DIY bio-nitrate filter because it was clear I could no longer use my well water and continue 50% weekly water changes. My thinking is that if I can keep nitrates very low AND otherwise increase filtration, I could reduce the frequency/volume of water changes whether I buy or make DI water. I think DI water will be my direction. Actually the well water nitrate discovery caused me to seriously rethink filtration and water changes. (but I'll bet you got that from the other thread
You have a clear advantage of good, low/no nitrate tap water. Once you get your nitrates under control AND change your bad ways and do regular water changes, you should be good!
Now you'd think that if you did a 50% water change w/zero nitrate water, you'd chop your tank nitrates in half and after a few of these, they'd be gone. It didn't work for me. I did several 15-20g water changes on my 60g tank over a week or so and I couldn't get nitrates to come down at all. I resorted to using Fluval Nitrate Remover to get them down. Nitrates in my tank have now been stable for nearly two weeks at 10ppm. I can't say this is the filter as at the start of this I also added 3 bunches of anacharis floating plants that are doing well and I'm sure help with ammonia. I'm hoping with the filter to get to 5ppm or less nitrates, but think I'll need some patience for that.
I'd say you can try a 50% partial water change daily or every other day and see what happens with your nitrates. If I was you, on the first one, I'd do an aggressive gravel vacuum and service your filter (shut down any nitrate factories).
If that doesn't work, I'd do a total tear down/clean-up, taking care to preserve the substrate and filter media with moisture.
Keep us posted.