Heater placement in sump question

I have always had freshwater with my heaters in the tank. I will be converting to a saltwater tank with a sump filtration system. I have read where many people place their heaters right in the sump. Wouldn't this cause the heater to run almost constantly because of the constant flow and reintroduction of cooler tank water? I realize it is all the same water but isn't that why you buy a certain wattage of heater per gallon tank size for when the heater is in the tank, but my sump is significantly smaller capacity than my main tank.??? Wouldn't this mean you are using more electricity($) than necessary? Help me understand this!

 

The volume of water and its ability to retain heat will ensure that with the right size heater and adequate flow, the entire system will maintain a constant temperature, regardless where the heater is placed.

 

I agree with Mr. Bill all the way. You also mentioned buying certain wattage of heater per gallon tank size, so make sure you go with total volume of water and not the DT. It is the same concept.

 

When buying a heater I prefer to think about the required temperature change between ambient and where you want the temperature in the tank to be, not a watts/gallon rule.

 

OK, I was thinking along those lines that the total gallons per wattage is what matters but I just had a hard time thinking that the fish tank is going to drop temperature quicker without a heater element actually in the tank. I plan on trying to lay my heater in the sump tank. Thanks for the replies.

 

I prefer to use 2 smaller heaters then one large heater. It gives me one more fail safe =-)