Manny
Small? I have some with near 4 inch stalks and 3 inch tentacle spans. But, I am raising them too. I've had them 2 to 3 inches in a couple tanks. Big or small, they sting the tar out of many corals, small seahorses, small fish and clams. They start out really small.
Larry, the thing I'm seein is maybe like 1 or 2 mm big. It "lives" in a small hole in my mex turbos shell. It looks just like the picture you posted but you can't see the base cause it's in the hole. Is it possible for a baby aptasia to be living on my snail or is it something else?