sentences:  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.A "biotope aquarium" is an aquarium that is designed to simulate a natural habitat, with the fish, plants, and furnishings all representative of a particular place in nature.Because only species that are found together in nature are allowed in a true biotope aquarium, these tanks are more challenging and less common than the other themes.