You really need air filtration to oxygenate the water. Use tap water for the initial setup, let the tank sit for a couple of days with the filter running before you put fish in it. Fill a one gallon jar with tap water and let it sit for at least 24 hours. You'll need it as the water in the tank evaporates. Just remember not to "shock" the fish. All water must be room temp and no clhorine. Do not use any kinda chemicals to clean any of your equipment. Keep the tank away from direct sunlight or you'll be cleaning algea off the glass every week. Get small fish. Big fish = lotsa shit = more cleaning......cleaning a 25 gallon tank will be an all day job. Neon Tetras are cool, they're eyes glow like headlights. When you buy new fish, remember to let the plastic bag float in the tank for about an hour so the water in the bag levels out with the tank water.
That'll be $100.....next.