Ammonium Bicarbonate

My question and/or situation:

I have been playing around with ammonium bicarbonate dosing my tank for about 6 months now; however, I'm constantly running into nitrates being near zero--like 1-2ppm. I used to keep my tank around 10-15ppm before ammonium dosing and was having great success. Does anyone have experience with ammonium dosing? If so, did you find that your nitrates tended to run lower than when you nitrate dose? I keep my phos around .07-.15ppm. I shoot for .1 ppm but allow for some small variance.

More information: I had a pretty bad tank crash back in February due to underestimating my alk requirements with sps (probably, most likely, long story), but my tank is back and running stronger than ever. However, I lost my initial batch of SPS. I've been slowly reintroducing SPS into my tank--being more picky about which pieces this time--but my tank is currently fairly flowerpot heavy (gonis and alveopora).