Hi Cecil- Just curious if you could not use a large bladder/pressure tank or a couple of them in series? 40+gpm might be a bit much for most residential tanks but if you can it back a bit I am sure it would work. The tank in my house that I put in is just over 80 gallons and I know they make them even larger. You can also bank a few of them together if you were to want as long as the bladder pressure is identical which isn't to hard to do. You could then have a pressure regulator on the output side of the tanks heading to your acuaculture setup. Even if you only needed 10pgm there would be big savings for you in the amount of $$$ to power the pump and cutting it back even further would be all that more of a savings.

Next year I am going to get another pressure tank like the one I have in the house just for my recirculation system as it will cut my jet pump running by 80% which will make my wife very happy! and the $$$ savings will pay for the $450 pressure tank by the end of the summer (Our hydro rates are crazy and I was using $65/month at a constant 4gpm inflow and I would like to bump it up to 8 for next year)

Ryan