A study of a fish farm with rapidly growing rainbow trout in the ocean showed that 78-82% of the phosphorus feed to the fish was lost to the environment. A second aquaculture study using normal fish foods showed that 62% of the fed phosphate was released to the environment, with 35% being released as soluble phosphate available directly to algae, and 27% as phosphorus in fecal pellets (which if not removed, will break down in an aquarium releasing the phosphate again). Another study showed that 81.5% of commercial diet phosphate was released to the environment, but that with a "special" diet with low phosphate and low fish meal this could be reduced to 64% lost. A fourth study showed that growing fish fed slightly less phosphate than they need (to optimize theoretical uptake) take up and retain different phosphate sources differently. Using a purified protein diet, they observed retention of 72% of the phosphorus, 51% retention of phosphorus from added fish bone meal, and higher levels of uptake and retention for inorganic phosphate supplements (such as sodium phosphate).