Heh, when my arrowana would yawn, it looked like you could almost put your whole fist in there. Except for that bone spike thingie at the back of his throat, that would hurt.
And pleco blinking is very expressive looking is'nt it? I wonder what it means...
I always wondered if they do it to suck in a lot of water to clean themselves out or something. I know - weird idea - but it just seems like they're so refreshed after they do it. Like if I had one that looked unwell, and suddenly it "yawns" then it is always a sign everything is back to normal.