As plants grow and multiply they will consequently begin to compete for resources (e.g. light, nutrients), and thus growth rate will be reduced. Periodic thinning or harvesting is required to reduce competition, thereby ensuring that there are adequate levels of all essential factors per plant. Periodic thinning is particularly important for water hyacinth which displays density dependant mortality (i.e 'self-thinning') at very high densities. Algae (planktonic and benthic) will often compete successfully for light and nutrients with higher aquatic plants, particularly in water with a high nutrient level. Therefore, good algal control is essential and achieved by;

	avoiding over-fertilising ponds,
	ensuring that ponds are fully stocked with aquatic plants to reduce the amount of open water available for algae growth, and
	using shade cloth/covers.

Algacides should be used only as a last resort, because, depending on their concentration, they damage not only the algae but also the culture plants.

Periodic thinning of aquatic plants is required to reduce
competition.