Then, should I put a background on my aquarium?
A fish tank background is one of the most important things that directly influences the behavior and color of your fish. It is best to put the background on two or three sides of your tank to reduce the chance of your fish seeing their reflection and becoming stressed.
Moreover, is it OK to put tap water in a fish tank?
Water and Water Quality. Ordinary tap water is fine for filling up the aquarium as long as you let it sit for several days before adding fish (the chlorine in the tap water will kill the fish). It is a good idea to let the filter run for a week before adding fish to the tank.
Trim the background to match your measurements, by using a razor-sharp knife or scissors. Clean the outside of the glass thoroughly. If your tank already houses fish, avoid spraying cleaning products onto the glass, so they don't splash into the water. Spray the cleaner onto a cloth and wipe the glass clean.