In addition to degrading the tank's appearance, algae can pose a significant threat to fish and other aquatic life. Algae can also crowd the environment and severely threaten plant life by competing for nutrients and blocking light.
Ammonia is released directly from fish and invertebrates along with solid waste and urine.
This organic waste together with decomposing aquatic plants, algae, and fish food, can increase the level of toxic ammonia in an aquarium. Generally, ammonia is detoxified naturally by biological filtration. Two species of nitrifying bacteria are responsible for biological filtration. Nitrosomonas species convert ammonia to toxic nitrite. Nitrobacteria species convert nitrite to relatively harmless nitrate.