I ordered PVC coated 1/4" hardware cloth. Hopefully that will work and I'll monitor the health of the minnows after I build and use my first cage. If it turns out to be less than desirable, I can still find other terrestrial uses for the cloth as I am constantly using that kind of material and chicken wire for other projects. If I ditch on that, I'll get some kind of netting that is softer and more pliable.

I think I will build a square or rectangular shaped box but will round the corners.

One idea I would like to use that I hope will work for breeding spots is to add a bunch of cut pieces of corrugated 3" or 4" tubing inside. I don't know what size diameter would be best and also am wondering if I need something with a rougher surface area for the eggs or if that would suffice. If I can go with 3" tubing, I can fit in more spawning spots. Also I can get either solid or perforated walled tubing. I am also unsure how long I should make these tubes, 4", 6", 12"? I don't know what would be more effective for breeding and egg laying while also trying to utilize as many locations for them as possible.