I needed a better way to hold fish while sorting or seining, so I went with a holding box instead of a cage. Holding boxes are used more for hatcheries than ponds, but I've had several and really like them if you're only wanting to hold fish for a few hours, or a few days.
The only real difference in a fish cage and a holding box are the sides and bottom, which are free floating on the holding box(free sinking actually), and are nonrigid. This makes them extremely easy to transport and deploy once in the water.
This holding box is 5X5X5, and I used 2" pvc for this one. I added a double top to it, and the 1' of free board should help keep most jumpers in the box. Tilapia and grass carp are the exceptions. I also added the double top to increase the instability of the holding box. GBH shouldn't be able to stand on the box and eat the contents.
I got the net custom made from Miller Nets, and if you take into account all the time zip tying or lashing of rigid plastic fencing to the pvc on a cage, the bulkiness when moving a cage, and the ease of assembly, the price was right in line with a more conventional cage.
This pic shows the net draped on the pvc frame, and clips holding the net on the top bar. I decided not to permanently mount the net, so that I can take it off and store it inside when not in use. It also allows me to adjust the depth of the net as needed, so this one is good for 1' to 5' deep.
This pic shows the 3/4" aluminum bars that once in the water, will keep the bottom of the net spread, and add very little weight at the same time. I connected the bars to each other with 3/4" refrigeration tubing.