Phosphates in an aquarium do not directly damage the fish. However, they affect the aquarium in an indirect manner. High levels of phosphates can cause a spurt in the growth of algae. Algae absorb oxygen from the water. This affects the health of the fish.
Algae growth also affects the clarity of the water and the appearance of the tank.
Uneaten food, fish waste and dead fish are the biggest source of phosphates. Keeping your tank clean is an easy way to keep phosphate levels within limits.
Planted Tanks also have lower phosphate levels and the plants absorb the phosphates and the inorganic phosphate levels are brought down.
Phosphates can be kept in check by frequent water changes. Special testing kits which measure the phosphate levels are available. However, these kits measure only the inorganic phosphates and not the organic phosphates. Organic phosphates are the phosphates which are part of the cell structure of plants and fish.
Scraping algae growth inside the tank. Rinsing the tank equipment in clean water and vacuuming the tank to remove fish waste, uneaten food and other debris can also