It depends on what type of setup people have to keep water readily available for there deer. If you have automatic watering systems, I strongly suggest cleaning them out with a small amount of bleach, then rinsing the water. You both hit the nail on the head when you said it will kill off the good bacteria. No sense in doing that, you might as well leave the deer with some water that is a bit dirty. I have seen some farms that take 1/2 a 55gal drum and use that for there deer. These work pretty good, they just tend to grow that nasty algae if not cleaned out on a regular basis. I would think a small amount of chlorine would be no different than tap water. Before I would do anything like that I would most certainly do some research so I did not give my animals dangerous levels of it.