[MCsaxmaster]

There's a lot of merit to your line of reasoning. The way I would suggest as helpful to interpret this phenomenon is that greater resource availability/flux (to a point) tends to increase the length of food chains and the potential for biodiversity. Increasing biodiversity tends to reduce waste and improve efficiency of a food web. Hence, even though one may be feeding more and there may be a lot more creatures in the tank a well-fed, biodiverse tank may actually produce less waste (which needs to be removed) than one with sparse feeding and low biodiversity.

cj