Really cant figure out what makes them split.Thought it was lack of light, nope .It split on a full moon,and on a Thurs.!Only the mother splits though,none of the clones have.Igot it from a friend ,who had it for years.Never split.They are wonderers though,all over the tank .That's why I had to take them out of my display.They will come together every now and then.They use their tentacles to split.It looks like it is cauterizing itself right in half.