I think smaller enclosure would be better at start. About earthworms, my vet says they carry parasites, so it would be better if you would stick to small crickets and cockroaches. And yes, chubby frogs, like all amphibians need powdering with supplements. I use dendrocare and repashy vitamin A for my chubby frogs and currently waiting for these fatties to breed, they seem fine, despite of being WC frogs. Yours is WC also probably?