you cant be too afraid of anerobic bubbles. its bound to happen, but you can reduce the possible damage. cycle the tank for about a week, during which you poke the the dirt with a chopstick or something to release anerobic buildups. after that you can plant plants with extensive root systems. these fast growing plants will reduce the extent of anerobic bubbles. flourite will always be better, and MORE expensive, but you can have success with miracle grow.
Hope this helps!