It’s uncertain whether an emerald would touch it. Emeralds can cause other issues long term, namely become aggressive to other fish and inverts. I wouldn’t get one unless the problem is getting out of control.
My LFS talked me into getting emerald crabs: "Oh, just get like a dozen crabs and they'll clean up the GHA in no time!" So I bought six. They didn't touch the GHA as far as I could tell. I started losing snails which I blamed on the crabs (I sort of caught one red handed trying to flip a snail). One by one the crabs disappeared until only one was left which I banished to the sump. Crabs, or any other critter, is not the magic bullet with algae.