Problem: I have a 2 acre pond from which the water exits via a stand pipe (vertically 10' then horizontally 70'. The stand pipe has become clogged with vegetative material (I left out the ounce of prevention). We have exhausted plans A - F of attempts to mechanically remove the clog with zero success. Plan G is a chemical "draino" plant dissolver, but one that won't harm the schedule 40 pipe. I don't know what cocktail of chemicals I can pour into the stand pipe that will go down, stay down, dissolve the clog, and not kill too many fish. Thanks for your expertise.