This used to really bother me too, until I did a bit of research on the chemistry involved and gave it some thought. I use a python on my 150g tank--it's in a business, and I do big water changes to keep the organics under control, and having several dozen gallons of water lying around for several days isn't an option. I add enough water conditioner to treat the whole tank, not just the water being added--that's important. I also have the filter running. So, the water conditioner gets circulated through the whole water column, and the chlorine/chloramine gets instantly nuked as it contacts the aquarium water. I doubt the fish ever get a whiff of it, and it's certainly neutralized before it gets into the filter or the substrate. No problem.
Anyway, my angelfish have not embarked on a campaign of militarization (at least not anymore than what you'd expect from a school of angelfish), nor have they set up any concentration camps to try to exterminate the tetras, so I guess we're doing OK.
