So what is the best process for doing a water change with a tank using an overflow box? If I drop the water level much, it stops overflowing, and since the pump outlet pumps the water out of the box, it quickly empties. In my case, I put my heater in the overflow box, so it overheated the other night when I was doing a water change. Obviously next time I can turn off the filter, or perhaps add a siphon to draw water into the overflow while the water is lower on the other side.

Or can I just do small water changes over time? Or is it important to remove a full 20% or so and then replace it?

Michael