You're welcome. Part of the club thing is sharing knowledge and experience.
I think it's safe to say that my original critter was a flatworm, species undetermined.
Flatworms are an impressive group of creatures. There are more than 20,000 species, roughly half of which are parasitic (including the tapeworm that infests human intestines) and the rest predominately predatory. A number of species are quite beautiful resembling brightly colored nudibranchs without the frilly gill appendages (flatworms have no organized circulatory or respiratory systems - all gas exchange occurs through the outer membrane of the animal by diffusion).
Without flatworms, humans wouldn't be here. Flatworms are our evolutionary ancestors.
Flatworms were the first to develop bilateral symmetry (a left and right, body structure mirrored down the center of the animal). That's right folks, all bilaterally symmetric animals (including humans) descended from flatworms millions of years ago.
Flatworms also pioneered three layers of germinal tissue (ectoderm, mesoderm, endoderm) which are still part of human embryonic development. Roughly put each of those layers gives rise to different parts of us. The endoderm forms our digestive and respiratory system, mesoderm bones and organs, ectoderm our nervous system and skin.
So respect the flatworm. And kill the ones which consume Acropora.