my boyfriend tolerates it, and keeps reminding me that we don't have room for another tnak right now.
he calls it my obsession. but i tell him, well you have your little hobbies, this is mine. could be worse, i could come home every week with new shoes or outfits or hairdo instead of fish.
tell her its your hobby, and she has hers. if she doesn't have any, tell her to get one. if she loves you, she should be supportive of your interests provided you aren't doing anything illegal or that could harm you or others. and as fish keeping is fairly harmless, she really shouldn't have a problem. unless of course when she starts talking you walk over to your tank and start cooing to your fish or ignoring her over your fish, or the fish come before her. then i say she has a right to be a bit upset (and to look at you funny, cooing to your fish.....)
she asks you to kill them? you need to sit her down, explina these are your pets. asking you to kill them would be like asking her to kill her cat or dog for you. you need to talk to her about this, make her understand that she has nothing to be jealous over about your fish, they're your pets, your hobby, but they won't come first over her. thats probably what she's worried about, you care more about little scaly critters than her. reassure her thats not the case. of course, if that is the case, and the fish are more important to you than her, then why are you worrying?