Oh, as far as inverts for your bog, scuds, isopods, pond snails, and ramshorns are all good choices. Not only do they thrive in those conditions, they also feed on uneaten fish food and other particles that may escape the filter.
IF they escape my stock tank pond they will die in a waste land of dry earth and 112+ degree heat and in wetter seasons the pond is situated to far from the local water source.