Oh I know you can sell them, I accidently sold one I was meaning to give Hazel since she didn't have it yet.
I just... when the hell did we start dying in animal crossing? Okay FAINTING but still. Also I was scared it would send me back home after I spent nook miles on that ticket, but it just sent me back to the dock the plane was waiting at, at least.
Fun fact, if you take it out of your pockets and place it, instead of a fishtank, it's in a swimming pool. A swimming pool.