Aquarium filtration apparatus; Germicidal lamps; Ionization apparatus for the treatment of air; Ionization apparatus for the treatment of water; Ozone generators for sanitizing purposes; Ozonizers for sanitizing purposes; Purification installations for sewage; Reverse osmosis membrane filters for water treatment; Swimming pool chlorinating apparatus; Swimming pool filters; Water filtration apparatus; Water purification installations; Water softening apparatus and installations; Water sterilizers