The past decades, animal welfare has become a very important part of any zoo (as it should be). However, it's very clear that not every group get's the attention it deserves. Whilst large mammals are often subjected to strict standards, reptiles, amphibians, fish and inverts often are somewhat ignored. I have yet to see an aquarium for example that doesn't have multiple setups that are clearly quite stressful for the fish, for example many cichlid tanks which house way to many territorial fish inside them or tanks that are simply too small. Sharks are also often kept too small, like the blacktips in Antwerpen who are probably unable to mate because the water level is too low. Crocodiles often have very little room to move, especially the larger species. Snakes are often kept in terraria where they can never stretch out, whilst there has been a study showcasing that this is actually quite important for the animals. Snakes are also commonly kept together though this can and has lead to snakes being killed/eaten by conspecifics if not done carefully. Turtles are often kept in groups with a lot of aggression, resulting in stress. I've even once heard that for most species of turtles (especially tortoises) it's advised to have no more then 5 turtles inside the enclosure, although I did not find the original source for this statement. Inverts on the other hand, especially tarantula's, are sometimes being kept in enclosures where they can barely move at all. On the other hand there are also enclosures like the Anaconda-enclosure in GaiaZoo, the rattlesnakes in Burgers' Zoo and the nile-crocodiles in Blijdorp that really stand out when it comes to reptiles. I would think the pond in Amazonica (Blijdorp) on the other hand is an example of one of the better fishtanks, with very few individuals and lots of space for the large arapaima. Most tanks in Burgers' ocean also come to mind, like the shark tank that's not filled to the brim or the eagle-rays kept without sharks. I'm interested what other examples are out there of both good and bad enclosures for these groups, and what actually defines the difference between the two. It might also be interesting if some reptile-veterans could share what they find to be the greatest and most often sins in zoos.