Hi Rodger, from my experience...the 'blue' tilapia are pretty tough fish.

I help a guy raise them commercially. I catch them every 10 days and check for fry and/or eggs. Yeah, they get a little stressed, but shortly after doing it, they are ready to eat again.

One time, a buddy and I were transporting some large ones in a 55 gallon barrel. He thought I tightened the ratchet strap..and I thought he did. On the second turn, the barrel rolled and they fell out on the road... We tossed them back in the empty barrel, went back to my place and added water. They lived and had a great story to tell their little fry...

It's not 100%... but often, you can pick out the males by the rear fin being reddish. Once they are in a glass tank...you learn their behavior and that helps too.
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