Valonia/Bubble problems

[DEAD_BY_DAWN]

For a brief history
aboout two months ago i was asked to help reclaim a marine aquarium,from bubble algae the tank was infested with the stuff from top to bottom after a few hours with a hose i managed to remove 75% of it last week i was called back to find 50% of it had returned "not surprising",
apart from emerald crabs is there much else that can tackle this problem long spine sea urchins perhaps ? any ideas would ber great thanks john..