First off you already getting them something that is restrained by glass telling them they can’t touch what they care for and that nature is meant to be admired and never tended to. Second of all Fish being low maintenance prepares them to settle for less and because the upkeep of fish is so miniscule when they eventually die you basically just allowed that child to think they can’t handle basic shyt such as feeding and changing of water. Teaching them about water systems and filtration is too complex and too much for them to manage despite the fact it would sharpen their critical thinking skills thus when the fish dies they would realize they weren’t the sole reason behind it