Help! my Pleco is acting really strange (?)?

Sounds like he is just comfortable with his souroundings. I had one that did that a few times a day. He has had no reason to be afraid. I am surprised he got used to living in a clear tank with all the extra light and outside activity, but thats good. the oscar might be a problem when it gets bigger, ive never had one, but from what I here, it could be just fine. I guess that last part is not very helpful, but good luck anyway :-j