Welcome to AA.
First of all, no more fish until you've completely read and understood the nitrigen cycle.
Manage your freshwater aquarium, tropical fishes and plants: Nitrogen Cycle for Dummies
Cycling takes time, usually around 3 weeks to 5 weeks. So that you kill no more fish, (per the title), i suggest reading the fishless cycle post here on AA.
Tips and tricks for your fastest fishless cycle!
Definately get yourself the API Freshwater Liquid Master test kit. Worth every penny. I would also suggest NOT using your city tap water. There are tons of chemicals that are harmful to fish and good bacteria. Instead for such a small tank I'd advise using RO
water from a local fish store (lfs
) that might sell per gallon. Usually around 50 - 75 cents a gallon.
Once all that is done, and you start seeing nitrAtes, you can then think about adding your fish.