analysis of macrophyte water hyacinth (eichhornia crassipes) as an organic fertilizer of colossoma macropomum (tambaqui) larvae in ponds is provided. water hyacinth produce an organic fertilizer at the ratio of 100 g.m-2 in tambaqui ponds. two groups of 5,000 larvae were transferred to two fishponds with and without water hyacinth fertilizer and reared until day 43. the fertilized pond evidenced more plankton abundance during the entire production period when compared with the control pond (p < 0.001). the phytoplankton community in the pond was not significantly different than in gut contents (p > 0.05) in both ponds (with and without organic fertilizer). fish larvae failed to show any preference or selectivity in relation to the different algae (p > 0.01) in the pond, but exhibited high ingestion selectivity for zooplankton (p < 0.05). application of fertilizer increased (p < 0.05) the abundance of phytoplankton and zooplankton in the treatment pond. since water hyacinth fertilizer is quite cheap and easily available, it may be conveniently used to enhance fish yield in ponds.