So far I think it is a Plexaura Flexulosa, a gorgorian coral.
I am losing this specimen (at least the lower third of one half of its branches lost its polyps, exposing a dark brown rigid skeleton) probably to my tank being still new (e.g. not enough macroalgae to keep phosphates below 0.1ppm) and with inadequate water circulation (my surge bucket is still being tested and I am using standard powerheads at the moment) and likely
iodine depleted. (as a rule of thumb I don't dose what I cannot test for, might be harmful or still confused about).
It requires a somewhat complex (at least to this day to me) water circulation pattern: water movement should be perpendicular, reversing (alternating), and laminar (as opposed to turbulent, swirling flow).
I intend to return it to the ocean in the same spot I "rescued" it (now I know I shouldn't have) and see if it can survive, unless it is not a good idea (environmentally wise) to place a specimen that lived in a tank back to the ocean (any risks there?).
Pepetj
Santo Domingo