Actually, we tried the container thing with Goo as well and he could have cared less. He was always much more interested in watching us, trying to find ways to get our attention or observing with more excitment re: whatever was going on outside the tank vs. than anything inside. He never tried to *escape* from his tank though - he was just extremely curious (not scared) about the activity going about in the room.
The previous octo, Ollie I, didn't bother much with a container either. Just looked it over, then let it be. Didn't even try to take out the little crab (and we know they were the preferred kind) even though it would have been quite easy to get it. One thing interesting Ollie I liked to play was a *counting* game of sorts. I would put my hand in the tank in one corner and Ollie would start from the opposite, come all the way across on the glass, touch me with one arm and then go all the way back. Then, would come all the way across again, and touch me with two arms and again return to the opposite corner. Then, come across to touch me with three arms, and again go all the way back to the opposite corner. This would continue, in consecutive order, until I would finally be grabbed by all eight arms. And, I gotta tell ya, it scared me a bit the first time.

I was grabbed onto with quite a bit of strength and I wasn't so sure I wasn't going to get bitten.
Unfortunately, Ollie I and the one prior to that (Tako) were before I really got involved with TONMO. I might have been 'wiser' about some of my decisions regarding Tako if I had been.
My only writing/posting about anything had to do with a silly, ridiculously backed, poorly written House Bill a silly Senator was trying to pass.

I didn't write about Goo until I was finally frustrated, or stumped about figuring out what species he was. And would have never figured it out either if it hadn't been this group. I had thought for quite some time that he was O.
rebescens and was worried about letting him touch me yet wanted to let him (they can have a nasty bite).
Anyway, didn't mean to babble on...
You if haven't already, you might want to pull the cup with the crab out. It's possible that the crab is dead (not good for the water) or Grendel doesn't like the cup in there (thinks doesn't go with the decor - maybe into modern indie look and it's too *plasticy* )

which could possibly keep him/her on guard. Don't know, just a thought...
Hope things continue to progress positively though and I think eating is definitely positive.