I had valonia in my 33 gallon, and tried just about everything to get rid of it including emerald crabs, manual removal, and eventually popping them.
The only way I got rid of them was when I switched all my rock over to my new 125 gallon tank, flipped all the rocks upside down crushing and burying all the valonia into the sand, and I have never seen them again.
have no idea why that worked, but it did.