One of my fishy clients just brought me a goldfish that has it's mouth stuck open. I can't tell if there's anything stuck in his mouth or not. Any thing else that could cause this? The client is a newbi and has been trying to get his tank cycled and I'm not really sure how that's going. I've been advising that he test every other day and trying to teach him but my first thought is water quality issue. Is there anything regarding water quality that could cause something like this? I put him in a quarantine tank in really good water with another goldie for company. Not really sure what else to do at this point. If he was a koi I could get a better look in his mouth but he's only about 3 inches long. I don't even think I could get a tweezer in his mouth if I could see something stuck in there.