A new study published in the Journal of Fish Diseases says that it is inadvisable to feed lower phosphorus diets to fish.
While phosphorus is an essential component of the diet, too much can increase phosphate levels resulting in an increase in algae. As a result, some manufacturers are deliberately taking special measures to cut phosphorus levels in their diets so that the foods result in less phosphorus-rich waste polluting the water.
However, a lack of phosphorus can lead to problems with the bones including rickets and skeletal malformation, and to metabolic disorders and issues in the conversion of the food energy into growth.
The report says that there is a growing trend towards diet that provide lower levels of phosphorus to reduce P levels in effluent from fish farms.
"Many variables influence P requirements and P availability in fish diets, so it is inadvisable to feed diets formulated to an assumed minimum dietary requirement level, irrespective on the advantages that such a formulation may provide to environmental impact."
For more details read the paper: Sugiura, SH., Hardy, RW and RJ Roberts (2004) - The pathology of phosphorus deficiency in fish. Journal of Fish Diseases. May 2004; 27(5): 255-65.