Care, maintenance, critters

I do not have a specific question yet. There are so many things to deal with. We do seem to have a constant outfall, perhaps less than 10gph during the heavy summer months (100 degrees F) with no visible inlets. Winter sees 2 or 3 inlets and maybe 10gpm outfall. The weeds along the bank are a total hassle, there are two fresh intermittent water otters who destroy everything - i almost want to shoot them. Anyway, just looking for what you all do to keep yours functional. Oh, it is maybe 70' x 40' oval, max of 5' deep, rarely very clear. We do not want to dump funds into it.