Careful research, as well as your own personal interests, should be your guide in deciding the types of aquatic animals that you buy for your aquarium. Unfortunately, modern collecting methods and modes of transportation have made readily available scores of species that are completely unsuitable as captives. All too often, these animals perish relatively quickly in captivity, without having reproduced. Yet the demand remains unabated, and so continued collection pushes the species ever closer to the brink of extinction.