Keep in mInd for a large tank emerald crabs often do not get the job done. Ime they do not live that long. The red sea sailfin tang, and actually many other tangs and rabbitfish will take to bubble algae. My sohal tang keeps it under very good control in my 400 galllon system, but sohal's need a lot of room and can be mean to other fish.
I bought a few emerald crabs for my 90 and had no luck. Best method that kept mine in check was manual removal. I use a 1/3 in hose and create a siphon. I use the end of the tube to pop and pry the algae off the rocks. I always keep the siphon going so any spores are sucked out. You'll need to be able to move the rocks around, but it tends to be on areas that are better lit. I dedicate 5 gallons of my water change each week to hunting new bubbles. You can put your thumb over the tube to stop the siphon when hunting for new patches and will buy you much more time.