hm...
How long have you been adding water to your tank without a dechlorinator? You may just have chlorine in your water, which evaporates after a little bit of time (usually around 24 hours with some arration from what I've heard). Phone your water company, ask them if they add chloramines to your water. If the person who has answered you cannot give you a definite answer, get him/her to hand the phone to someone who can. If you have chloramines in your water, a dechlorinator is needed... you want one that can break the chloramine bond, and eliminate ammonia. I use Seachem's Prime to dechlorinate my water.
Water treatment for a planted tank, and a non-planted tank is exactly the same. The only difference in water chemistry between the two tanks is, in planted tanks, you add fertillizer (there are exceptions), and in non-planted tanks, you don't.
HTH
-Richer