Last year I built several 8' circular "pens" out of that plastic barriers netting. These pens held around 10 pairs of 3-6" tilapia. I then made it a point to throw feed to them once a day. They bred prolifically and nothing got to them. The holes were more than big enough for the free swimming fry to swim through. The whole thing cost me about $50 and it is reusable.
Best part? It was incredibly easy to net those fish out of the pens in the fall and overwinter them in my barn for next winter using a closed system. This year, I put them all back in, but no pen needed. They are about 12" and several pounds! They can take care of themselves.
I did this because it can be hard to get tilapia early enough in Spring and they can be expensive now.
Just a thought.
