People will debate on whether it's okay to gently touch your fish or not because some believe it removes their slime coat, leaving them prone to infection. But let's not debate that here. I'm wondering why koi seem to be the only species of fish that don't mind you sticking your hands in their water, even petting them. I know they want to suck your fingers for food, or just have you feed them, but they seem to really not mind/enjoy the attention. Some family friends have a koi pond, and they're completely pet-able. They have no problem when you pet them, even seem to enjoy the interaction. I just don't know any other fish species that have this personality. My fish enjoy looking at people through the glass, and know that opening the lid means it's feeding time. They'll even eat off your fingers (bloodworm juice), but there's no way you could pet them. Don't worry, I've never chased my fish around the tank trying to pet them. I just know from doing water changes.... Just a curious question is all. This video is a perfect example.