I think another question to add to yours is, "is it morally acceptable to keep wild caught fish, and non "domesticated" fish species?" As we know, very few fish are domesticated in the sense of being modified from thier wild form physically and behaviorally such that they would probably not survive well wild and "need" man to continue. The only ones I can really think of are fancy goldfish, and some betta tail types (maybe some guppies, but I'm disgustingly uneducated about them). Is it ok to keep species other than these, particularly if they are wild caught, as you are essentially keeping a captive wild animal? And, especially in the case of ocean fish, that you are keeping a captive wild animal that may be threatened in the wild, and yet was wild-caught?