I keep extinct in the wild and critically endangered species of fish in my aquariums and am a member of a couple of fish focused associations who work with universities for the goal of preservation of species. been considering getting into red listed frogs and cactus, but the communities are smaller (so less access to species) and space is a premium when living in an apartment.

i wish there was more exposure of this hobby because it's such an affordable, easy and "low effort" thing to do, but a lot of people who care about the environment and animals basically get offended when you keep animals "locked up" in an aquarium. in my opinion, serious aquarists (not the pet store furniture mentality) are invaluable, as a lot of species has been saved from extinction through aquarist efforts and university collaboration to reintroduce them to their native ranges after restoration work is completed (at least Lenoardo DiCaprio made a little bit of social media impact for one of the associations in 2022).

I should add, overfishing is not the leading cause for extinction in freshwater fish, it's pollution from agriculture, as the vast majority of fish threatened with extinction have no utility to us (or bright enough colors to benefit the commercial pet trade - brightly colored species are generally not even found in the wild, and have their colors from decades of selective breeding by dedicated aquarists).