Most cichlids, for example, especially the larger species from Africa, South and Central America, love to move, dig and channel the substrate. One look at the mouth structures of cichlids and you can see why they are efficient gravel movers. Therefore, when choosing gravel, it is better for the fish to have a thick layer of smooth pebbles, similar to their natural habitat, rather than sharper, coarser stones that can possibly injure mouth parts and result in infection or permanent damage. An effort should also be made to find out what types of plants are native to the waters of the fish that are being kept. These plants are often vital to fish in their natural habitats.
Some fish use plants as a spawning medium.
They will also deposit eggs upon other hard surfaces, but these particular plants are preferred. Plants are often an important part of a fish's basic diet. In addition, plants provide shelter and protection from predators. In some instances, certain plants give off substances that have a bacteriostatic effect, protecting fish from various bacterial infections. On the other hand, there are plants that may be inappropriate for some setups.