I have had good luck with emeralds eating the smaller bubbles, I have also used a sharp piece of rigid tubing connected to a hose and siphon out the insides of the bubbles when doing water changes. I had also read that they release spores when they are popped, but when an emerald eats them, they are popped. I used the sharp tubing on half of my tank 2 months ago, and they haven't returned on that side. I also had a phosphate issue then and have since lowered them, so that could also help.