I will be collecting my moon jellies from the ocean so I will be able to choose what sizes I like, They live for few years and it take a couple years before they reach any where near the one foot mark, Also when they do get too big for my system I can just return them to the ocean and get some new ones. The upside down jelly requires more work than the moon jelly since they are much more sensitive and need very strong light to survive where moon jellies don't need any light.