Tank has been up for a couple of months now and all of a sudden my nitrites and nitrates spiked ! My nitrite is at .10 ppm and nitrate is at 12.5 ... Are these real bad levels ?
Nitites should be zero, although .10 ppm is not that high. Nitrates seem to be a little high but not life threatening. I've seen mine hover around the 20 ppm for weeks and then drop after I change the filter pads and do water changes as well.
I'll probably get flamed for this, but I feel that you'll be fine as long as you acclimate properly (drip method). I would not suggest adding any fish right now until the nitrites come down since it would only add to the problem.