Sure, Bubbles the all-of-a-sudden-genius doesn't sound a bit like himself, and I wanted them ALL to have some significant moments/lines in the film (there are seven of them, they're like a Star Trek crew...or The Baby-Sitters Club...)--but, this little scene alone would have been 9,999,999% better than the little logic-challenged post-credits blip we received. The Gang deserved to be in the film BEFORE the credits, and they were pretty much the most exciting thing to me, alongside Dory's story itself. Confound it all! Even without Dory, such a subplot would have greatly enhanced the film!
I can accept what was included, but it can only be truly redeemed with another sequel or short film. So y'know what, since this exists and they REEEALLY didn't want to have to eliminate it, I am going to right now officially decide that it DID go down this way. Mission Impossible Tank Gang #SquadGoals, helping Marlin & Nemo rescue Dory...before getting captured by the institute themselves, then escaping, and then fiiiinally meeting up with Marlin/Nemo/Dory/etc. at the frick-frackin' Great Goddamn Barrier Reef. AIIGHT??!? Sound good?? Eeeeyup!!
Eta: Just took a closer look at Nemo's classmates in this shot. You've got a parrotfish, and a yellow/purple one up top that looks like some kind of striped variation of the Bicolor cherub (Centropyge bicolor.) I love the color combinations here--seafoam+lemon on that generally butterflyfish-shaped one, the green-spotted yellow guys, the purple+red crab...I just can't understand why they, like Lisa Frank, included a combination of actual species and made-up ones. Real tropical fish are so stunningly beautiful and artistic-looking that there's no need for people to draw randomly-colored and -patterned "new" ones, though that happens all the time.
Thankfully, almost all of the speaking characters in Nemo & Dory are real species.
Of course Nemo, Pearl, Sheldon, & Ted are (Amphiprion ocellaris, Opisthoteuthis californiana, Hippocampus kuda, Forcipiger flavissimus.)
Edit: Judging from the art book, they should have not only included the deleted tank gang scene but also shots of little Blenny the psychedelic fish (Anchor's "fish friend" from the shark meeting in Finding Nemo), cow- and/or boxfish in the kelp forests (FOR SURE; Ostraciidae is one of my favorite families, how could you POSSIBLY even consider omitting those wicked-awesome dudes?!? Especially when you're spending so much time in KELP FORESTS?!?), and certain other interesting-looking (if not actually real?) creatures I don't recall seeing in the film.