I think it really depends on a lot of things, such as species, how endangered they are, how carefully they are being collected, and how damaging it is on the environment they are being collected from. My main concern is collecting saltwater fish. These fish go through horrendous conditions to reach our aquariums, and we can't do much about it considering the majority of saltwater fish are not being raised in captivity. Luckily, most freshwater fish are being bred in captivity so we can buy from the better sources. I will admit to having some wild-caught specimens like otos and amano shrimp, but I always try to find tank raised animals before buying wild-caught. But as long as there is no danger to populations and environment and the wild-caught specimens are kept ethically, I'm not against it.