Can I put this rock in my aquarium??

I wouldn't suggest putting phosphorus. I would think that the water would leach phosphates into the water. It is true that all living organism contain phosphorus. Phosphorus is an important element of life as a component for cell membranes, as an energy source, and for other bio-chemical processes but it is usually counter productive in aquarium water. Phosphorus is a very reactive component making it readily absorbed by water and generally always available in aquatic environments as either an organic or inorganic phosphate. Generally the measurable phosphate level should be below 0.05 ppm. If levels of phosphate are too high in aquariums you can look forward to blooms of algae and diatoms. Algae will grow with phosphate present in ppb (parts per billion), so only a limited amount of phosphates are necessary for algae to grow.