hi, i have a 120cm aquarium and i am considering my heating options. i have one heater on my 120cm and i have to have the 'lily' pipe type outlet pointing at it in order to get the heat around the tank. therefore on my new tank after considering a hydor ETH and deciding it is to costly i am considering running two heaters. interpet say 1 300w heater will do a tank of my size (240L) but i am considering running two 200w heaters. will this be overkill or can i get away with 2 150W?