When catching big fish, like deep sea fishing, I have always used a shot of vodka, or any full strength spirit down the gob to smack the lights out of any violent fish. fish gills put alcohol directly into there blood system making it truly the poison it is. Its like if you bypassed your liver, wouldn't take much booze to kill you either. Hence why I have never seen a good reason to pour alcohol or any "unnatural" substance into my aquarium, despite its use. So I would say in your system the alcohol would probably react off before it was able to do much damage to the fish, otherwise youve got some fish who need to see AA... ahaha