If it's going to be outside, just do what I wish I could do, put in like 10 mosquito fish and let them populate the entire tank so everyday you can be amazed and happy that your fish are breeding, plus you're harvesting your own bait for fishing trips and you'll never have a mosquito problem. =) Plus they take the cold weather pretty well so maybe all you'll need is a basic heater and an air unit. Filtration could just be a big pile of anacharis at the bottom or something.