Zoos, including aquariums, are hot points for discussion and debate for people unyieldingly pro and con about their existence. I'm not a fan of zoos and would like to see them phased out, however, in the "real world" this isn't going to happen anytime soon. So, of course, as long as zoos exist, we are obligated to give their residents, whose freedom is severely compromised in many different ways, the very best lives they can have. Treating captive animals with respect while working to close down zoos is not an incompatible goal.
A recent essay in New York Magazine by Benjamin Wallace-Wells titled The Case for the End of the Modern Zoo is a very thoughtful essay that should be widely read and discussed. This piece was motivated by an essay that appeared in the New York Times by Alex Halberstadt called Zoo Animals and Their Discontents, also well worth reading. Some people will love these essays and others will write them off, but they do raise many of the important issues that need to be openly discussed. Mr. Wallace-Wells notes up front that he loves zoos. He writes, "My daughter is not quite 2, and the zoo brings out all of her best and least complicated emotions–awe, delight, empathy." Yet, he advocates closing them down.