We're all set.
I threaded the rope through the top of the net today and then attached the blanked off pvc piping with cable ties for buoyancy.
We tested this in the pool and it worked like a dream.
The chain hugged the bottom while the pontoons stayed afloat, extending the net from the surface to the bottom. You can see at the deep end the chain was suspended slightly above the bottom of the pool.
The wife's frog enclosure has been cleaned out and is well on the way to being filled with water to contain the good fish during operations.
This is all getting pretty exciting.