A tank like that could actually support my dream marine...a reef community big enough to support an octopus adequately!
Wow! My grandfather's was like that except deeper than wide.
He had liverock I am sure...and anenomes, starfish, weird snails and slugs and crustaceans. Sponges, pretty clams and then the fish..
he had one ocotopus... and one moray eel (I would think he small beautiful eels like fairy morays would be nice..)
He had damsels? all kind of tangs and parrot looking fish (trigerfish?)
And reef dwellers like clownfish. Siiigh! It was wonderful.
For the other tanks..he can keep stuff most people wish they could.
he could actually keep lungfish and arrowana and bichirs in true comfort. The big tank he could even try breeding those beasties!!(need a wire lid on top ^_^ or one of those rollout breathable hot tub covers)
I would use one of those" little " tanks to set up a killer biotope for just tons! of colorful
FW schooling fish like cardinals and neon tetras like suggested earlier. That would look sooo cool!
Or keep a really sensitive and rare species because the water volume alone ensures the quality some weird thing needs!
Maybe he should contact some kind of species maintainence program and get something really weird.
That's my cent and a half; the possibilities are bogglin! Now to go ponder aimlessly in the INSANE thread