I have a garage aquaculture system that i use to overwinter tilapia as well. So i am understanding of your goals. I dont try to get them to spawn in my garage system, is that one of your goals?
Usually the numbers in crowding is enough to protect the fish from aggressive males.
If you want fry to live you will need to consider a couple of things
1) some sort of protection from predation in the ibc, and
2) some way to keep them from going into the aquaculture plumbing (or an inline trap to catch them once they leave the ibc through your drain.
This is an intex pool but i have also done overwintering in IBC. I have 200 in that 900 gallon pool. I have don 40-50 in a ~250 gallon ibc
brian
