Mark, Glad to see you here! I think you made a good decision on raising them out in a bare bottom tank and that 75 gal will give them plenty of growing room.
Red wigglers can be a great food item. I used to have several cultures going here at a time for both my fish and amphibians. I should probably start one up again for my critters. Glad to see your fish are enjoying the blackworms!
I hope you can post updates as these grow, It will be interesting to see how pigmented they are as adults..Do you know what strain(s) the parents are? Looks like a few are non pigeons ?
Welcome again!
Al