goldfish with sore/swollen mouth

Question
tank is 5 gallons and has been up for 2.5 years (same age as my fish).
he is presently and has always been the only fish in the tank. typical filter - just cleaned the tank (half of the water, gravel clean, and filter change about two weeks ago).
all water specs are fine

my poor goldfish "Fish" seems to have a swollen mouth that doesnt shut all the way. he can still eat with some difficulty, but he seems to be doing well otherwise. there are no visible leasions, rot, etc. It just seems like his mouth was twice it's normal size when i woke up this morning. (he almost looks like a parrot fish now).

any advice or insight you can give us is greatly appreciated.

sincerely,
Carla & "Fish"  

Answer
Hi Carla;

It's possible he has a rock lodged in his throat. Look inside and see. You may have to lift him out of the tank to do so. Be sure your hands are wet as you handle him and hold him over the tank so if you drop him he falls in the water. Gently open his mouth with your fingernail, a chopstick or a soft thin piece of non-splintering wood. Don't let him be out of the water for more than a minute. Dunk him back in the tank to let him get wet again as needed. It can be difficult but if you can rotate the rock with a chopstick hopefully he can spit it out again, if that's what's wrong. I hope "Fish" is okay...

At Your Service;
Chris Robbins