Thermolux heating mats are made of water proof and rot proof materials are absolutely watertight and can be used without any danger in freshwater they offer maximum safety due to the built in full surface protective conductor always remove the plug from the power socket before cleaning the mat or working on the aquarium to prevent danger of electric shocksthe mats are connected by means of the plug direct to the 230v power supply and at an ambient temperature of 20 c and without a cov