Why no filter? A sponge, or box, filter would be good. You could run it in the main tank for a week or so to build up the bacteria before putting it in the fry tank.
Could be a number of reasons but I would suspect stress from being in a breeding trap. I personally do not like the traps and would not use one. You are better having a heavily planted tank with lots of fine leaved floating plants for fish to hide in.
Well done Peter!! I do hope that once you get going you affiliate to the FNZAS. Do you mean Pets n Things will give discount to FNZAS members or only to members of your soon to be formed society?
Did all the goldfish come from the same place? My book suggests perhaps a flagellate infection of the gut. This is if "one or more fish are continually dark, ranging to black. They stand apart from the others and do not feed anymore. A slight bloating is often apparent."
A small area going black, thickening and scales standing out can be a mailgnant growth but I doubt all the fish would have had one of these!
Have you tested the pH, ammonia and nitrates? I can't think of any of them turning the fish blotchy black though
Guppies usually breed continually. It is best to have a ratio of 1 male to 3 or more females so the females don't get stressed by the males chasing them all the time. It is possible (probable) the females you bought were already pregnant. They can produce 3 or 4 lots of fry without a male once impregnated. It is possible your male guppy isn't up to the job. Try another one. Don't bother putting them in a breeding trap to breed though.
Guppies can drop fry every 3 - 4 weeks. Breeding traps aren't such a good idea IMO, too stressful for the female. A tank with lots of fine leaved plants for the fry to hide in is much better. Java moss is good as is water sprite floating on the surface. The fry hide in the long fine roots.
Do you mean the red body bit or a red shell? The pic doesn't show what a nice bright red it actually is. There are lots of them in a guy's pond in Kaikoura and he had been told they were native.
Welcome Peter. Help those others pull their collective fingers out and get a group up and running in BOP! There are enough of you up there for a good group.