Okay. Two days ago I noticed my oscar as he/she swam towards me stopped and the top part of the tail fin vibrated.
I thought it must have done this to get rid of a bit of loose plant from his back, but the next day, I noticed the same thing. Just a quick up and down motion. I tested the water and everything's alright. He doesn't seem to be ill from anything, no new fish in the tank. A very happy O.
Anyway, I was watching a show about crocodiles and noticed that when trying to attract a mate, the crocodile, underwater shivered his back to make vibrations underwater to reach females.
Is my O trying to find a mate???
I don't think there's anything wrong. I tried to film it but my video cam is not that good.
What is it?

Funny ... my green terror will do that when the water quality isn't what it's supposed to be, or I've seen other fish doing it when they seemed to be "itching", but since you said the water is fine, it might just be such an Oscar thing. Haven't noticed it with mine yet, but from what others say, they do a lot of vibrating and fin twitching when trying to mate. Maybe he wants you to come in there and lay some eggs?
Hope someone else has a better explanation, but the idea cracked me up now:lol:

HAHAHAHAHA....my sister said the exact same thing. He comes over to me when I'm watching him and shows me his tail, then shakes it!! I don't think I'll fit in the tank though!!! Hehehehe