hi,let me start by saying i'm pretty sure we're way overloaded on fish.we have a 140 gallon 2 pc pond(37 top drains into a 103 bottom).it currently has 3 4in shubunkins,5 3in comets,7 4in koi,5 tadpole,1 9in goldfish,a bunch of snails,freshwater clams and mussels.also water hyacinths and other plants.the big goldfish has to go,but the rest are pretty small and seem to be doing great.i have a tetra pond bio filter and a uv light.i'm getting string algae in the top pond but not the bottom.anyone have any ideas?i'm open to any suggestions,i'm very new to this.