Rainwater collection is super easy and is great for the environment. If you live in an area with a water shortage, this is also a great way to make your water go further. You can create your own pretty easily, but most of the commercial options are built to prevent stagnation and keep mosquitos...
I would suggest getting some aquatic plants that help to effeciently filter the water naturally. Have you ever seen a "natural" swimming pool? they are for all intensive purposes a pond that has been sanitized and oxygenated through a simple pump and plant system that is safe for swimming. They...