hello,
welcome to nano tanks!! I also have the 12 gal. aquapod.
I love it. I guess I should ask how old your tank is. Nitrate problems are fairly normal if you have a young tank.
Heres what I did with mine:
In the first chamber on the left I have the sponge (I think it came with the tank). I cut about 1-2 " off it and on top of the sponge I place a bag of purigen. (small bag costs about 8$). In the second chamber I have my heater and my pump in the last chamber (which I upgraded to a maxi-jet 900)
The first year I tested EVERY day and did a 1 gal. water change with RO water EVERY week. It took about 4 months (after my oringal cycle of coarse) my nitrates went to 0. If they went back up I would do a larger water change (2 gal.)
My tank is 3 yrs old this christmas.
Hope this helps!