Hope I'm in the right place for this. This is something that I have been thinking about for a while now. Would it be possible to use a large planted tank as a filter to a main display tank? I have been thinking about using an old 135 as a planted sump filter to my larger tank. That would be a 135 gallon planted sump on a 240 gallon tank. I would use no other filtration chemicals such as carbon. This would be the sole source of filtration. Any opinions? Would this even work? What kind of plants would be used?