That is what my green bubble tip looks like lately. It was originally very big and not so green. It went into hiding for several months and when it finally showed up the other day it had split and gotten darker. The lfs
says that some anemones get darker if they are in a deep tank or don't get much light. I actually thought this one was dead months ago and was very surprised to see it again and doubled. However it definatly does not look like an aptasia and if it were me I would not get rid of it unless it is multiplying profusely. Actually looks kinda cool.