My experience is that a little Remedy & diesel mixture will kill them (the senna beans) although mine were in wet areas, not in a tank. I can't remember what the label says about fish, but it probably says to avoid use near fishing waters. Nevertheless, as to the fish, I worried about that some when I applied Remedy/diesel to a bunch of huisache that was growing all around my tank, some on dry land when the tank was low and some that were still in the water, but to my knowledge I never had a single fish die as a result. At the time the huisache were of much greater concern to me than the fish. The tank didn't have bass, but did have cats, hybrid bluegills, fathead minnows, etc. Just try not to get much of the mixture in the water. Either use a backpack sprayer to carefully spray the lower 2 feet or so of the senna bean bush -- or affix a semi-worn out paint brush to a piece of wood and "paint" the stem. (read the Remedy label about the basal stem method). Try to get them killed out before another seed pod crop is made.
On the other hand, if you like to hunt doves, there's nothing better than a September tank shoot where you hide amongst the senna bean bushes and ambush the doves as they come in for late afternoon water.
