However, the results were disappointing, perhaps because of defense mechanisms in the plants. The last form of control attempted was mechanical destruction. This was costly in time, money, and energy, and several of the procedures used damaged the ecology, affecting all animal life in the ponds infested by the hyacinth. On many occasions it has been demonstrated that this weed is an excellent water depollutant for domestic water wastes. The results of several studies show that plants such as the water hyacinth use appreciable amounts of the inorganic forms of nitrogen and phosphorus found in domestic sewage.
Some papers report high levels of growth hormones such as gibberellins in the roots.
The fibrous component might be useful as a base for a biogas-producing system. Methane-producing bacteria require such nutrients as nitrogen, potassium, and phosphorus. Many studies have shown that the water hyacinth provides these elements in the quantity and proportion adequate for good growth of bacteria and for satisfactory gas production. Another possibility for the use of water hyacinths is as a source of pulp and paper. As an animal feed, it has been used fresh.