Zoo Med 3 Pack of Betta Mopani Wood, Mimics Bettas' Natural Habitat. Zoo Med's Betta Mopani Wood is a natural wood item that is designed to make the water chemistry of your Betta tank closer to what a Betta would experience in the wild. By placing this small piece of Mopani wood in your Betta tank it will naturally leach “tannins” which will give the water a light to dark brown tint plus lower the pH of your water. (Bettas in the wild live in water naturally tinted by decaying wood and leaves and with a lower pH.) Should the water be too dark brown or not to your liking you can remove the Mopani wood and soak in a clean container of water continually changing the water until the shade goes from a dark brown to light brown or clear.