that trype of pump is normerly used in ponds for either fountains or for waterfalls. it can also be used for water features in gardens, like statues that have water comming out the mouth etc, or bubbling rock type things.
some people use that kind of pump in sumps, so the water can be returned to the tank.
Yes. I have a setup that makes use of a water pump for doing water changes, although my water pump is in a 25 gallon domestic tank that has been setup in a cupboard for water changes, has a heater in it so the water is kept at 25C.
Be aware that the pump will stop working as soon as the inlet is uncovered, so you wont be able to get the last few inches in the bucket, so maybe a bit of a waste of time.