Not done it for tank use but for other uses, it is much the same as moving other liquids, so I might throw out some ideas.
Any chance of setting the reserve higher than the outlet at the tank? If you could do that, the problem becomes much easier as it will siphon, even without pumping. The top of the water level at the reserve will have to be higher than the outlet or the water level at the tank to make it work but if speed is not needed, I might look at tubing like used for icemakers, etc. and just go with a small valve to shut it off at the tank end. Float switch at the tank end like is used in the drainpan for AC unit condensation tied to a tiny solenoid would make it almost auto fill as long as the siphon is held?
Do you need a semi-quick flow or is slow going to work? Bigger hose works quicker but smaller hose is easier to run through the walls, etc.