Be patient, you can convert them over to Repto-Min. Feed a little R-M with a nightcrawlers for a while. Then gradually reduce the worms while you increase the R-M. These frogs are unique in that they are scavengers as much as predators. Your aquarium should support 4 ACFs. I wouldn't worry much about the males bullying the females. Females grow larger and mature faster than the males. I have a alpha-female that had to be separated because she was bullying the males. Mostly, they get along pretty well. Having a floating island is an interesting idea. Let me know how it works out. In the wild, they often migrate from one pool to another when their home dries up. So they do travel on land for short distances. I haven't figured out how to de-poop worms, that's why I stay away from the big ones. You can feed the live or frozen/thawed bloodworms or blackworms. No freeze-dried worms! If nightcrawlers work for your frog, then go for it as long as there is a steady supply.

Temperature is a big concern. These frogs like it on the cool side, around 20 degrees celsius (give or take a degree). If it's too hot, they will not thrive. Mine are kept a room temperature all year around. Those who keep other species, like Xenopus muelleri and X. tropicalis like it a little warmer. Enjoy your frogs!