Question: how big do aiptasia get?
Answer: The “stalk” or the coelenteron (polyp body) as it is more correctly called of the Aiptasia can grow up to 5 cm / 2 inches long. The disk at the top can grow to be 2 cm / 3/4 inch wide. The coloration in the Aiptasia is caused by the dinoflagellate alga living in it.