UV lamp in an aquarium is the simplest type of filtration. It requires no special skills to operate, making this method of water purification particularly recommended for beginners. The lamp works by emitting UV radiation, which effectively eliminates harmful pathogens, improving the microbiological cleanliness of the tank by removing harmful fungi, viruses, and bacteria. Some UV lamps can eliminate life-threatening diseases for fish and also remove algae that cause water to turn green and produce unpleasant odors. The sterilizer for the aquarium is placed in the internal filter or is connected to it. The size and power of the UV lamp for the aquarium depend on the tank's capacity. We determine the frequency of the lamp's operation ourselves by observing the water and checking its parameters using tests.