I have never had an emerald eat it. They "say" the male emerald{bigger claws} will eat the small ones, but I've never seen it. I just manually remove it. If you are very careful, you won't break them. Saltnoob is right, there is some extra nutrients fueling it. Best way to eradicate it is good water quality.{not overstocking too} Check your phosphates, nitrates, and alkalinity.