When looking to figure out what to plant, you have to first decide what your purpose is.
Are you building an aquaponics set up to grow your own food? To build a business and sell what you produce? Something else?
If looking to raise your own food, decide what you use the most and would most like to have, then test to see what works best for your setup, situation, location and needs.
If looking to raise food to sell, start looking through the area, talk to people who might be the buyers for the produce you expect to grow. Ask them what they need, what they most want and what is it that they may be having trouble getting in locally grown produce, especially out of season if you are planning to build in a greenhouse or indoors and can produce year round.
Once you get an idea of what will sell, and an idea of what kind of prices that produce will bring, start your testing. Build a small unit for testing and see what you can grow best, what has the fastest growing schedule, etc. Your testing, along with your research, will tell you what you can produce at a profit, and how regularly you can provide it.
Remember, if you plan on growing commercially, it is easy to grow, the real business is to grow what you can sell at a profit.