No problems with circulation or Temps. Just water changes. When you change water, and debris in the sponge above the waterline tend to fall back into the tank.
It's like picking a sponge filter up out of the water, it bombs the tank with debris. Other then that, the disadvantage is fish always find a way behind them. Jumping over , or around etc. I realize in your mind you're thinking, just cut it tight... Trust me I did... and they still find a way. At the wet spot in portland oregon, they have them installed in their sales tanks and have the same problems.
That said, they do have a ton of bio capacity.