If you want to have a saltwater fish tank, it is much easier then you might think. I didn't say it was easy, but most people can have a nice one without too much trouble.

The first step is making sure you have plenty of fresh clean water. You need to buy a reverse osmosis deionized water filter also known as a RO/DI filter. It takes all the chemicals, nitrates, and other impurities out of the water so you can make clean fresh seawater.

Here is a quick video on one way to install your filter and store your fresh water.