You guys are killing me with this scientific bullshit.
I have seen many lakes that smell fishy. My Grandfather was a fresh water commercial fisherman. Know why the water smells fishy. Because they are filled with fking fish. Most fish need oxygen to survive. If that lake has fish it has oxygen and vegetation. Damn near every lake gets runoff from ppl. Go figure. That doesn't mean the water is poison. If it was the fish would die.
I think sometimes we try and over think growing weed. I have watered my plants with all kinds of water and you know what killed some of my plants,,a fking DOG.