Many people buy fish as a cheap, low-maintenance pet. They mistakenly believe fish are easier to care for than a regular pet, that it is natural for them to not live as long as other animals. The reality is, we don’t really know much about how to care for tropical fish. Scientists haven’t done enough research on aquatic life. But they’re a popular beginner pet used to teach kids responsibility and to brighten up pet-friendly apartments. That leads to a lot of mistreatment by owners, and the pet industry.