Just a general question that never really occurred to me. I started out with an HOB but I quickly made the switch to a sponge filter and haven't looked back. It's become a force of habit to turn off my filter and heater during water changes. I understand why it's completely necessary to turn the heater off, but what about the sponge filter? Could I just leave that running without any serious (or any) issues arising? I assume because there's no motor or parts that would suffer if it ran out of water it would be fine? Just a wondering question.