Why the buckets? Thats just going to hurt flow because you are no longer in a closed loop and also cause you to lose water. Not to mention that you won't be able to use water wetter unless you don't mind its midly toxic vapors filling your apartment.
As for horizontal distance, it won't jelp, but probably won't make much difference with a good pump. I'd use an Eheim 1250 myself. The outside loop could make a huge difference if you live in a cold place.
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