Honestly, I don't really see a marine biology degree doing you all that much good when it comes to running your own business regardless of whether or not it's aquatics related. Also, if you're thinking more along the lines of doing wild harvesting of tropical / ornamental fish it would help some but not all that much.
In a marine biology program you'd learn much more regarding the science behind our oceans. You'd definitely have a good background when it comes to where to find a specific fish, it's native habitat, requirements and breeding behavior are but I also think that most of your classmates and professors would probably frown upon using a marine bio degree to harvest tropical fish.
I'm planning the same sort of thing. Instead of traveling and harvesting the fish I plan on opening a pet store specializing in exotic & aquatic pets and importing breeding stock. Where captive breeding isn't possible I'll import my stock fish. There are a great number of people all over the world that wild harvest or breed fish for export. Personally I'm pursuing an "Individual Studies" degree program concentrating in chemistry, biology & microbiology. My school also offers credit for individual research projects and I plan on doing a couple semester long research projects related to marine / aquarium life. Concurrently I'm also pursuing a one year certificate in small business management in order to give me the basic accounting, legal and organizational skills needed for a small business.
Whether you choose the marine bio route or another degree program I'm sure you'll learn a lot from it. I also think that college is a great way to network. Keep it in mind when you're going through school. Getting on good terms with a microbiology or bacteriology professor may be useful later on when you have an unknown disease wiping out your fish and you want a definitive identification of it done in a lab for example. Never underestimate the usefulness of college prof's even after college is over. ;-)
G'Luck!
Ric
