natalie265 wrote:
"The ammonia reading you are getting
> from the tap is probably from the chloramine used to treat the water by the
> city. Chloramine is a compound chemical made by bonding chlorine and
> ammonia. Treat the tap water with dechlorinator, stir it well, then test
> it."

Spot on. Also just to note: If for any reason there were ammonia in your tap water (not very likely at all) it would drop very quickly in a fully cycled tank.

In my fishkeeping I've rarely used anything other than dechlorinator and aquarium salt as additives.