I don't know about lifespan but they are not delicate. Lol they don't drop dead in Petsmarts care I wouldn't consider them fragile.
I would go with a cute arapaima...buggers only get about 4" AT MOST! Nice active little guys
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ah, didn't realize they needed to be in groups, that would be a problem.
Colefishing: I've been searching around the web, but I'm not sure if those spatula barbel catfish need to be in groups or not. Planet catfish has a few posts on them, and most people are keeping them in groups of 4+. Not sure if they're ok to be kept alone or not