I have 52 hatchlings right now that are ~2.5 weeks old. I'm going to attempt to raise them together, but I have containers to separate them should there be a problem.
Currently I have 6-10 hatchlings separated by size in 12"x9" food-grade containers I got at the dollar store. They're ~3/4-7/8" right now so not too big. As they get bigger, I'll decrease the number of hatchlings/container to a)keep water parameters better, and b)decrease likely hood of axies coming into contact with one another. I think the key to success in group raising with as little risk to injury would be to feed each individually (I'm currently doing that with white worms cut in half), not leaving any food for them to have a spat over, and offer plenty of places to hide (floating plants,fake ones, etc).
Keep in mind keeping them as groups, you still need to do lots of water changes. Currently I change 40-50% of the water every 1-2 days, as well as scrub out as soon as you notice any of the sides getting slimey. I also poop-hunt with my turkey baster 1-2x a day. Doesn't hurt to do 100% water changes 1-2x a week, too, as well as scrub out the container (I just scrub it with my fingers using the old water).
I have a 5gal pail that I fill with close to container-temperature, add dechlorinator, then let it sit for 24h just to be extra cautious
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When they get larger I'll probably pick up a second 5gal pail.
Hope that helps/gives you ideas!