So I just finished setting up my 750g tank and I have multiple heaters that add up to 1300watts. I insulated my garage so that the temp wont fluctuate. I placed my heaters in my 180g sump and put carpet under the sump. But I am noticing that my heaters are on all day! How many watts should I have total so that the heaters are not on all the time? I was thinking that 2000 watts (2 1000 watt heaters) should be good. Has anyone used these types of pond heaters? I am thinking about buying them. http://www.heatingyourpond.com/submersible-heaters.html Lastly, I am thinking that having heaters in your sump may be less effective since only a limited amount of water travels through at a time versus in the tank where it is surrounded by all the water. Would you agree?