I have an Oscar that has stolen my heart. I found this site while trying to find out if he is sick. I really want advise to make sure he is okay.

Our tanks have been cycled for a long time with regular maint. He has never had a minutes problem. But he has recently started shuddering to a point he splashes water and disrupts his plants and the frogs. He opens his mouth wide and shakes like he is fighting a fisherman. Any ideas?

Up until a few weeks ago, I had a beautiful and 11 inch red Oscar, unfortunately she died. Anyway, I recall her doing exactly what you describe yours doing a few years ago (nothing to do with her demise, before you worry) it was almost as if she was having some kind of fit. Anyway, like I said this was probably three years ago and she lived for a long time after.. why they do it is a mystery. They could have something stuck in their mouth which they are trying to dislodge I suppose. Maybe even some irritation somewhere on the body makes them do it.

If the fish only does it occasionally and is okay the rest of the time, I shouldn't concern yourself too much

There are known accounts of Oscars eating barbed catfish and then having the barbs lodge in their mouths preventing the oscar from swallowing the catfish totally. I was going to ask you, do you have other fish in your tank and are all accounted for? It does seem like the oscar could be trying to dislodge something it partially swallowed or it could be something like what Penn experienced too.
Just rule out its not a fish he tried to eat.

-Especially raphael cats, larger plecos, and bumble bee cats. Basicly the ones with longer barbels.