Although plant proteins such as soybean meal contain sufficient amounts of phospho-
rus, about two-thirds is phytate phosphorus which is in a bound form (Lovell, 1977 cited
in Kim and Oh, 1985) and is poorly available to fish (Akiyama, 1988). Similarly in rice
bran, phosphorus is also present as phytate phosphorus and only 25% available to carp
(Takeda and Ogino, 1975 cited in Hepher, 1988). The beneficial effect of supplementing
phosphorus to soybean-based diets has been reported by Kim and Oh (1985) for carp
and Hung (1989) for tilapia.