Kar93, the "quick slice behind the head" method is actually severing the spinal cord. I read somewhere that only a vet should attempt it. Perhaps there is a vet or marine biologist reading this who would like to provide more info on this method?
Back to someone's earlier point, I recognize the danger of flushing algae or dead fish down the toilet, but isn't there plenty of algae cells in the water you remove from the tank while doing a water change? Don't most people flush this water, or am I just ignorant? Regardless, I live in Minnesota so I assumed that no algae that gets flushed finds its way to the ocean. Is that not right?