I love your passion and can certainly relate to wanting to get out of corporate life and pursue that passion full time - I'm in the process of doing just that right now, and I can tell you it makes you want to jump out of bed in the morning ;-)
You seem to be exploring two possible ideas - selling and servicing systems in your area, and designing software for the AP industry. You are smart in having multiple options as it will probably take a while to get either going, and you can be developing software in the off hours when you aren't working the other business.
For the design/build business, I'd recommend paying close attention to what Joel Malcom is doing with Backyard Aquaponics in Perth, Australia and I'd also try to engage Murray Hallam (who is a member of this community) who has also been an inspiring pioneer in the home-based aquaponics craze in Australia. Those guys are about 5 years ahead of anyone here, and they do a great job.
The software idea is very unique - I haven't heard of anyone else do that. Your best market will probably be commercial operations, and the people who have the best grip on that market are Rebecca Nelson and John Pade (Nelson and Pade). I recommend you contact Rebecca who is a member of this community, but she is too slammed with her very successful business to spend much time here. You could try from here, then try through their website at Aquaponics.com (yes, they got into this industry early and got the great URL!).
And to find other aquapons in your area you can go through "members" tab and see what you find. There are several. You may want to start a Florida group like I did for Colorado...
Hope this helps. I'll look forward to hearing about your progress!
I think it's great that a fellow Jacksonvillian is into aquaponics. I'm currently an active duty Marine in San Diego, but I was born and raised in J'ville (I-95 & JTB area).
As for your software monitoring, I'd love to see a product that would be used in conjunction with a Mac Mini and could not only track temperatures, but would also have a probe that could track oxygenation and such, and could potentially kick on a small air pump if a threshold is broken, send emails if pumps fail, or any number of things an owner would want to receive as an alert. Using the Mac platform, also lends the software to iPhone/iPad tools/push notifications, etc. Just a thought.