I hoped for the same thing, realized after a semester as a marine biology major that marine biology was completely a labor of love, and earning a living would be very difficult, reliant on grants, etc. So now I do real estate and spend the money I make on fish.
Something to be said for chasing your dreams though. I worked at an aquarium store in high school that I know for a fact is very profitable. This was because It was better than the other stores in the area, and the owner was incredibly passionate about the store and fish in general. And they have expanded into commercial aquarium maintenance. So, if it's really what you love, something like that would be do-able.