NYC tap water has orthophosphate added to it. Its actually not the worst thing in the world for your initial set-up, but the problems come in using tap water for your top-off. You are continually adding more phosphate....If you can't afford, or don't want, RO, just get a tap water purifier....all the aquatic supply places sell it, at pretty consistent prices...under $40.....replacement deionizer cartridges run about $16-19......That's what I use, and I only have to replace the cartridge every 3-4 months, as NYC tap water is about the cleanest that tap water gets. Get one ASAP, do a couple of water changes, run carbon or one of those phosphate removers (can't vouch for them, as I don't use them....not since my tanks earliest years) and make sure that your only top-off water is deionized or RO.