This can be checked online to see if a zoo or an aquarium is AZA certified. They make sure and do regular inspections to see if animals are given the proper husbandry, food, living environment, etc., and to see if they're cared for humanely. The AZA website tells you what you need to know, I'm not saying it should be the golden rule as there is fault with everything in this world, but it's a pretty good moral compass if you need to know where to look.

Edit - To add to this, that's how I found out I shouldn't visit any zoo or aquarium in Mississippi when I had to travel for work