This way you won't have to constantly treat the new water with additives. This also allows for a more stable environment for the fish. You can find out about your water at your local pet shop or a local fish keeping friend. Set it up right the first time and then leave it alone. Don't keep moving things around and fish in and out.
Big fish have a nasty habit of eating little fish.
You're trying to keep a simple aquarium. Feed only a small pinch of food every day for each 10 gallons of fish. Every time you feed the fish, think of it as adding fish crap to your tank. Get a low maintenance filtering system. When combined with the low stocking levels and light feeding schedule such a filter will last for years with no problems at all.