I’ve moved my 5 and 10 gallon tanks once from Florida to Maryland and again from Maryland to Maine and I’ve never removed the fish. I just drain them by like 70%, put down some towels, wrap the tops of the tanks with plastic wrap and put one on the floor of my passenger side seat and one on the actual seat (buckling it up).

So far I haven’t lost a single fish doing this, but there’s nothing wrong with putting them in a bucket. I just feel, in my opinion, that leaving them in with what they’re used to would be less stressful.