bubble algae size?

i have a lot of bubble algae one this one piece of live rock in my tank, my emerald crab is slowly eating it. i heard that if the bubbles are sexually mature they will spread when popped and the crab obvessly pops them to eat them. so how can i tell if they are sexually mature?

 

Ya, I have also heard time and time again that Emerald Crabs are good for bubble algae. But it is bad to 'pop' the bubbles when trying to get them out because the things inside will cause more bubbles to come up. So, I'm a little stumped too? Does the Emerald Crab eat the bubble algae whole? how does it eat it without popping it?