You cannot connect tanks with two pumps going in each direction. They will never exactly balance each other and one side will flood.
The best way IMO is to orient the pod tank somewhat higher than the main tank. Pump water from the display into the pod tank, and use either a drilled hole/bulkhead or a siphon overflow to take water back to the main tank.
Pods will often survive a trip through a pump, but you obviously decrease the number of deaths by not using a pump to take water from the pod tank back to the main tank. Most people can't do this because it's often far more practical to locate the pod tank lower than the main, but if you can work it out so it's higher, that's the way I'd go.