I have a been having a problem with air getting into the overflow U-tubes and affecting the flow. I couldn't figure out where the air was coming from so I spent a few minutes just watching it.
The air was from water spilling into the inside container and as it did it had air bubbles in it and would congregate in the U-tubes eventually slowing down the flow. It was caused by the rapid filling. I felt a simple modification would resolve the problem but I had no desire to experiment on trying to find the right one. I came up with a much simpler answer that would resolve the problem.
I took a piece of bulk filter material and cut it to be the same length as the prefilter but also taller. I inserted it into the prefilter and loosely wrapped it around the tubes and made sure it was all the way to the bottom. Not only does it break up the small air bubbles it also acts as another prefilter to stop large debris. By simply removing it during tank maintenance, it allows the debris to make it's way to the sump. At some point I will also experiment with using an AquaClear or Fluval sponge since they are close to the needed size already and have great water flow.
The air was from water spilling into the inside container and as it did it had air bubbles in it and would congregate in the U-tubes eventually slowing down the flow. It was caused by the rapid filling. I felt a simple modification would resolve the problem but I had no desire to experiment on trying to find the right one. I came up with a much simpler answer that would resolve the problem.
I took a piece of bulk filter material and cut it to be the same length as the prefilter but also taller. I inserted it into the prefilter and loosely wrapped it around the tubes and made sure it was all the way to the bottom. Not only does it break up the small air bubbles it also acts as another prefilter to stop large debris. By simply removing it during tank maintenance, it allows the debris to make it's way to the sump. At some point I will also experiment with using an AquaClear or Fluval sponge since they are close to the needed size already and have great water flow.
