has anyone got one of these heaters it can go on the intake side of an external filter so will tidy the tank up seems like a really good idea, someone has suggested that as it will be heating the water that is leaving the tank into the filter that it won't be as effcient as a normal in tank heater. 
/www.warehouse-aquatics.co.uk/aquarium-heaterschillers/rena-smart-heaters-c-199_91.html?p=shop







