The use of dirt in aquariums is not a common thing. However it can be a very effective method for growing plants. Dirt is the most natural plant growing substrate you can use. However if you do something wrong there can be frustrating results. There are some simple tips that can keep this from happening.
1. Use organic potting soil. Make sure it has very few additives, the more there are, the harder it is to cycle the tank successfully.
2. Only use about an inch of dirt in the bottom of your tank.
3. Make sure you put the same amount of a cap substrate on top of the dirt.
4. Use a small substrate for a cap, but not too small. bigger than play sand, but small enough so the plants can move it out the way to grow. (Pool filter sand is very good at this.)
5. Do weekly water changes until the dirt stops leeching a tea color in the water.
6. Wait about a month before adding fish. The fish will make cycling the tank much harder.
7. Add a lot of plants initially, this will help reduce the amount of nutrients for algae to use.
Follow these simple steps to make sure your dirted planted tank is a success. This is a picture of one of my newest dirted aquariums. Notice all the plants in the tank, this will help reduce algae. You can also see the pool filter sand on the right of the tank with the dirt beneath the sand.