Oh gosh - there's nothing wrong with you, I swear! Dreams are symbolic, so my guess is that it actually doesn't have anything to do with animals at all... That said, if my interpretation doesn't ring true to you, please let me know and we can work on it together.
Also - I have a couple of questions, but I'll try to work them into the narrative here.
First off, I think that the animals represent something in your life that you're nurturing - like a goal, or project. Since the animals are small, my guess is that whatever you've been wanting to pursue isn't something huge (like a new career), but is something that you view as a 'hobby' or 'side project' - it's not as if you want to change your entire life, you'd just like to dedicate more time to whatever this is. In your dream, you were having difficulty keeping the animals alive, which seems to say that this goal you've always harbored is kind of slipping away. Perhaps you feel as though you're getting too old to do it, or you tell yourself it's "silly." But your unconscious mind is telling you otherwise. It's telling you that you need to nurture this goal more to keep it going.
However, I'm not sure about the context in which you found yourself - the environment. For instance, was the fish tank clean and sparkly and beautiful, or was it cracked and dingy and in need of repair? These details might give me a bit more to go on. Additionally, how did you feel in the dream (not after you woke up)? What were you doing to keep the animals alive?
Thanks - I look forward to hearing from you!