I did test the tap water a while back and the only thing that was unusual was 0.25 ppm ammonia which I am assuming is chloramine although I am not aware that NYC uses it in the portion of the water supply they treat.
I run my tap water through a Brita pitcher before putting it into the tank. I don't have resources to let water sit so that seemed to be my best option other than treating it chemically which I am not a big fan of. I don't see putting chemicals into the water to get rid of chemicals. Just means more stuff in the water and my GH had been off the charts anyway but is coming down now.
When I tested the tap water I did four tests
1) tank water
2) old Brita cartridge
3) new Brita cartridge
4) tap water
If I am interpreting my notes correctly (I didn't mark which column of numbers was which since I didn't expect to need to reference them again but am going on the order in which the tests were done)
ammonia from the tank, tap and old filter was at 0.25 ppm and from the new filter at 0.50 ppm.
Nitrate was 0 across the board.
Nitrate in the tank was 80 ppm and from the filters and tap 0.
KH in the tank 2°, old filter 2°, new filter 1° and tap 2°.
GH tank 9°, old filter 2°, new filter 1°, tap 2°.
pH tank 6.4, old filter 6.2, new filter 6.4, tap 6.8.
On Monday evening I tested the water before I took roughly 50% out of the tank to put it into the new Chi. Nitrate then was the normal 60 ppm. The last 20% water change was 8 days prior.
I just tested the water again, 42 hours after the 50% change, and it is at 40 ppm with both the API chemical kit and, as a check, an API test strip.
I have never tested the water immediately after a water change.
My tank is heavily planted and I am going to have to go in there and get the fish some more swimming room. I have 20# Flourite mixed with 5# pebbles for substrate. I have a little packet of Hagen phosphate absorber in the filter. I alternately dose at each water change with Kent Black Water Expert, TetraPlant FloraPride and Nutrafin Plant Gro. Occasionally when I have been working in the tank a lot I will throw in a little API Stress Coat+. I have a chunk of mopani wood in there. My CO2 system is DIY.
I am overstocked, 200% according to AqAdvisor and trying to cut back on feeding.
The filter is stock with the sponge for an emergency filter sitting on top of the grill to the bioballs to hopefully keep some bacteria in it in case I ever need it. I also have a UV sterilizer in there but it has bern running continuously for the past six months so isn't producing enough UV go kill anything.