Aqua One GLASS water heaters are high quality and available in different sizes 55W (to suit approx 50L) 100W (~100L) 200W (~200L) 300W (~300L) Features High quality glass Can be placed horizontally as well as vertically in Hydroponic systems (vertically only in Aquariums) Thermostat is built in but due to localised heat effect you should adjust to temperature based on a thermometer set a little back from the heater to reduce on off on off rapid switching and faster temperature adjustment has a light to indicate on or off. All heaters should be used in conjunction with a working safety switch in the house