The small Fluval P-Series heater features very compact dimensions and an unbreakable plastic housing. The temperature of this heater is already fixed, so that no adjustment is necessary. The temperature in the aqaurium is always kept in the optimal range between 24C and 26C.Fluval Aquarium Heater P Series+ strong shatterproof polymer construction protect tank and inhabitants from damage+ preset temperate requires no adjustment+ waterproof, fully submersible design allows easy positioning inside aquarium+ LED running lamp illuminates to indicate when product is in use+ for use in freshwater and saltwater aquariumstechnical data Fluval Aquarium heater P10for aquariums up to 10 litreswattage: 10 Wpresetted temperature from 24-26Cdimensions: 13,5 x 2 x 1,5 cmtechnical data Fluval Aquarium heater P25for aquariums up to 25 litreswattage: 25 Wpresetted temperature from 24-26Cdimensions: 15 x 3 x 1,75 cmtechnical data Fluval Aquarium heater P50for aquariums up to 50 litreswattage: 50 Wp