A "planted aquarium" emphasizes living plants as much as, or even more than fish. Large groupings of plant species such as Hygrophila, Limnophila, Rotala, Vallisneria, Echinodorus, and Cryptocorynes with a limited number of fish is a good example of a planted tank. It is important to select fish that will not damage the plants, such as small tetras, dwarf gouramis, cherry barbs, zebra danios, and White Clouds. Planted tanks may include injection and a substrate fortified with laterite or, in the case of a low tech aquarium, a layer of potting soil under the gravel to provide nutrients for the plants.