Heater for 300gallon and sump return question

[Homer Siped]

So I'm in buying parts mode for my plywood tank, I have a friend that runs an inline coolant heater for a tractor in his return line on his turtle pond, roughly 300gallon as well. He has that plugged into an aquaponics thermostat. The one that I found at tractor supply is 1¼" in and out, first question is. Could I run something like this or better off with regular heaters, I have a jabao 15000 with around 5 ft of head pressure, I'm pretty sure it's 1½", and don't want to kill the flow. My second question is 1 or 2 return lines? And should I run 1½" all the way to exit?

 

[ragin_cajun]

Here's a thread where a guy posted the pump curve for your pump.

http://www.reefcentral.com/forums/showthread.php?t=2540839

figure you'll get 2400 GPH max with 5 feet head. I figure you'll have 2-3 90's in your pipe run, so you'll get less than 2400 GPH. I'd probably go with 2 pumps if I were you, and one output from each pump.