My fancy tail goldfish is 7 years old. The last few days he has been acting odd. He is in a 130l tank by himself and I recently done a water change exactly how I usually do it for the last 7 years.
He looks like he was gagging to be sick and his gills are flapping wide open. (This has never happened before) I had a look in his mouth for a stone or rock and couldn’t see anything. (I did this using a net so I could see right in) He is eating occasionally however not like before. I have also noticed today around the colour part of his eye he has black areas which are new.
Sorry to read about this. From your description, I would have thought he'd ingested some gravel. It's possible it may have gone further back / been swallowed, and he may try to pass it out the other end.
What are your readings for ammonia, nitrite and nitrates, using a liquid-based test kit? Although you haven't changed your tank maintenance regime, it's possible that the water supply maintenance has altered a bit, which can sometimes lead to alterations in water quality. Does your water company use chloramine and, if so, does your water conditioner address that?