Nitrate Levels

[n00b mariner]

I got a 5 month old tank and the nitrates are @15 ppm now after a long period of 20ppm. Could it slowly be going? I thought levels would increase? Maintenance has remained the same. Can some of you guys tell me how yours reached the magical figure of zero? Was it over time, instantly with addition of equipment or never there?

 

[rdmpe]

AFAIK nitrates can be reduced slowly by bacteria deep in the LR or deep in a sand bed where the O2 is depleted, or nitrates can be locked up by algae. Do you have a refugium with macroalgae?

My tank is pretty new but my nitrates are currently at 1.0, dropping from a high of 5.0 about a month ago. I assume most of this drop is from my macroalgae which is growing like crazy (caulerpa and cheato, 24/7 lighting). I'm hoping it will hit zero within another month.