Inorganic fertilizers were tested in combination with organic fertilization to study enhancement of zooplankton communities in largemouth bass (Micropterus salmoides) rearing ponds in southeast Colorado. Under study conditions, additions of triple superphosphate produced the greatest number of zooplankton/liter, a combination of liquid ammonium nitrate and phosphoric acid produced the greatest growth, and the highest yields were found in ponds treated with phosphoric acid alone. Triple superphosphate was as effective as liquid inorganic fertilizers in maintaining sufficient numbers of zooplankton and was easier to apply. Fish were returned at the desired length of 50 mm, which was longer than in previous years in spite of an increased stocking rate. Although total zooplankton/liter was lower than in previous years at the hatchery, cladoceran populations were maintained with no significant declines.
