Agree with Vaughn. Most, if not all potting soil contains a lot of organic matter and fertilizers. This will cause havoc during the first two months of setting up. You might be better off by getting cheaper top soil from HD or Lowes to begin with.
As the organic matter start to decompose, all the nutrients will leech into the tank water. As you start seeing the leeching nutrients, change the water. This will help control the algae explosion. After 1 1/2 months you can start slowing down the water changes and after 2 months or so, you can go a couple of months without water changes.
Good Luck.