Pump to empty and refill aquarium

Hi all,

I bought a 77 gal(US) aquarium a while ago and the monthly water replacing
is killing me! I would like to use a pump to empty and refill about 25% of
the water. I have a drain pipe that I can tap into about 5 feet above the
aquarium and the warm water bucket (that I fill up the previous day with a
nearby hose) for refill is about 15 feet away from the aquarium.

What kind of pump can I use to empty in the drain pipe (I can fit a regular
garden hose on it) and refill from the warm water tank? I suppose an inline
pump (with hose fittings at both the inlet and the oulet) would work...
What are you guys using?

Note: I do not want to use gravity or systems that you plug onto tap to
create vacuum. I would like to use an electrical pump.

Thanks!

Sly