Allelopathy is a term most often used in aquatics when referring to aquarium plants, although the principle can be applied to any organism. Allelopathy is the production of chemicals (called allelochemicals), which are released into the environment in order to adversely affect another competing organism and/or provide an advantage to the organism producing the allelochemical. In the case of aquatic plants, allelochemicals are produced to inhibit the growth or normal function of other plants and algae's. For plants, which cannot defend themselves in a mobile way (i.e. they cannot run, move or fight in the traditional sense), allelopathy is a particularly good way of becoming the dominant plant species in a local area. Producing chemicals to stop algal growth, and prevent neighbouring species growing in close proximity has obvious advantages. The production of allelochemicals is cited to be one of the major reasons why a well-planted aquarium rarely has algae problems, despite a high availability of nutrients and light. Allelopathy is often the cause of some plant species proving very difficult to keep in planted aquariums where all their needs are seemingly catered for. Unfortunately, little is known about the specific production and effect of allelochemicals on plant species so it is impossible to produce a guide to plant compatibility.