I have the exact same problem in my 150. I have also tried this method. It works but you really have to do it to all the rocks at the same time and make sure there are no aptasias in the over flow or sump. If there is any left they will start to pop up all over again. They are evil!!!! My plan is to just take out all the rock and replace it but only after I make sure there is no aptasias left anywhere. It's going to be a long process which is why I still haven't done it. I just have taking out some of the rock a little at a time. I have thought about just getting a file fish. But I need to get my tank in better shape before adding a fish to it. I have abandoned it since the aptasias have taking over. I must say that I did in the past have very good success with banner fishes eating the aptasias. But as soon as the aptasias are gone they will go after the coral.