You definitely can. I use a layer of aquarium fertilized soil (ADA aquasoil is my fav), a layer of peat and cap it off with gravel or sand for my native tanks. Then I boil some assorted dried leaves/pine needles/pine cones for about 1 hour and toss em in the tank while it's cycling. Within a week everything has sunken to the bottom and the tank is ready to go. The dead leaves host all sorts of beneficial bacteria and the boiling seems to negate any harmful oils that could potentially leach into the water.