An aquarium can be described as a closed artificial ecosystem where fish and plants find a habitat to grow and develop in a healthy and balanced way. However, residues from uneaten feed and animal excretions increase concentrations of ammonia and nitrogen, which can facilitate the spread of diseases and parasites. By regularly introducing beneficial bacteria into the water, these harmful compounds can be converted into essential nutrient sources for protozoans, which are then consumed by higher trophic levels.