big pump, little pump ?

[iansfishy]

I dont think the dart will push the twelve feet needed, and if it did it would be barely. I thought about a bigger pump like the hammerhead to do all the work ( CL and return) but that is at full open and trusting that some check valves on th CL will stop my tank from draining. I guess Ill go with two barracudas, just seems like alot of energy? But I guess if they are both valved down the energy consumption decreases as well. How come you can get more GPH out of a pump if you increase the pipe diameter? Does that still hold true if you say run 2 inch all the way then go down to 1 inch at the end? So after thinking about it for a minute does flow in the tank count as in the "tank" or total wter volume. For example- if the 180 has 120 g of water and i use a dart thats like 19 times turnover in the display thats pretty good. But if its total water volume like 250 g thats only like 13 or 14 times turnover/hour. but with a dart and having to go like six feet and 4 diffrent outlets according to the head loss calc from RC it cuts the GPH almost in half. I guess im looking for someone to justify my buying two barracudas! Thanks.