The heart of an aquaponics system is the fish. Tilapia grow fast (fingerling to plate sized in 6-9 months), like tank culture, will eat anything, and like the kind of temperatures I like. Plus they have a white, flaky flesh I know my family likes to eat.
The folks at Tilapia Vita Farms, aka Tilapia Farming At Home, have put together a guide to legal issues relative to keeping tilapia in each state. Living in Virginia, I must obtain a permit to "import, possess, propagate, buy, and sell" tilapia, and must provide
place of origin, the name and address of the exporter and a certificate from a licensed and accredited practicing veterinarian, or certified fish pathologist, certifying that the animal to be imported is not manifesting any signs of infectious, contagious, or communicable disease.
I can use mossambique tilapia, nile tilapia, blue tilapia, and/or zanzibar tilapia. The Virginia permits ($22.50 total) expire December 31st, no matter when you obtain the permits. So I plan to wait until January to get my tilapia. With the holidays coming up, deferring fish to January isn't much of a delay.
After fondly considering the various breeds and sources, I'm leaning towards nile tilapia. It sounds good to say this is because the nile tilapia is directly related to the fish of pharaohs. Alas, I'm just a sucker for the pretty white variant developed by White Brook Tilapia Farm. For better or worse, nile tilapia are the slowest to reach sexual maturity (16-18 weeks compared to 11 weeks for blue tilapia).
Even better, for my penny-pinching, internet-loving soul, I can get live White Brook tilapia via eBay ($25 + $89 S&H for 25 fry (1/2"), $50 + $89 S&H for 25 fingerlings (1")). That's $114 or $139 to you and me. Additional batches of 25 can be purchased with only a $5 increase to S&H.
Pros of other variants:
Blue tilapia can survive colder temperatures, down to 45 degrees fahrenheit. You can find these on eBay - I am impressed with White Brook Farms' descriptions and pricing (same as the white niles mentioned above), but right now you can get as few as five from another source for under $35 (fish + S&H).
Female Mozambique tilapia and male Zanzibar tilapia can be interbred to produce predominantly male offspring. Since a mature female tilapia can produce 200-1000 fry every two months, this can be an important consideration. Edgar Sanchez at Tilapia Vita Farms currently offers breeder colonies for $399 + $99 S&H.
Here's hoping White Brook Farms has nile tilapia available in January 2011!