The guy that originally had this tank said he had a 4200 on the closed loop and he could only run it about half way open. So I am unsure about going to that bigger pump.a series 4300 for your closed loop...
a barracuda uses close to 325 watts where a dart uses 165 watts. i did the calcs on .12 kilo hours and its something like $34 vs $14. its something to consider because you could run 4 darts with the electric to run 2 barracudas. i know you have head height issues and darts are lp compared to the cudas, but something to keep in mind.
a barracuda uses close to 325 watts where a dart uses 165 watts