gouramie. he does it all the time even when i am not looking.

we jsut changed the water and he's an old fish. he normally chills in the corner doing nothing. he barely even comes up for food. now he's still in his corner but he's actually moving in one spot and coming up to the tank. that fish barely moved at all before now he's coming up and moving......pH and amonia levels are good. he's one of the only fish in a 10 gallon tank. i don't want him to die or anthing.