As for your musing a few pages back, wondering if the Kraken was hitting the powerhead to make it work again, I was thinking that over...
I doubt that he was thinking "Oh, this isn't working, maybe if I hit it a few times it'll start working."
However... I have a pistol shrimp who seems to be smart, and that kind of got me thinking.
Maybe he'd sort of registered the powerhead as being good, as providing water movement, and then he noticed that it was no longer doing what it was supposed to. Maybe he then wanted to make it do its job?
I'm picturing a train of thoughts (probably more like images and instincts, the way I suppose most animals think) something like this:
Thing makes current. Good.
No current?
Thing not making current.
Bad.
And, being a smart creature, he responded to this in the only way a mantis knows how to respond to something not good; by hitting it.
Yeah, that does sound a lot like you were wondering, but I'm picturing it with pretty much no actual thought, just a string of- I suppose you could say ideas? I'm not really sure how to accurately put this into words...
That or it did that twitching thing powerheads do and it got his attention, so he decided to club it a few times.