a couple of questions for those knowledgable about dendrophyllia

[sirrus6]

Hi all

I recently purchased a coral colony labeled as "dendrophyllia" from Roe's Marine World. After 24 days in my aquarium, the coral has never extended polyps during the time that the tank light is on, but has extended its polyps when I have checked at night -- see pics below (In anticipation of questions, the tank is in my office, so I can observe it during its entire daytime light-on cycle, but I only occasionally have the opportunity to observe it when the lights are off and the room is dark.). I can feed it mysid shrimp successfully at night, but I could better ensure that it received adequate food if I could feed it routinely during the day.

dendrophyllia (?) under tank illumination (10K), 24 days in the aquarium



dendrophyllia (?) at night (with flash), 24 days in the aquarium


My questions:

1) Can somebody make an educated guess as to species (or even genus -- is it dendrophyllia or tubastraea)?

2) Can I modify my approach to its husbandry so that its poylps might be coaxed into opening during the day?

A few more observations:

1) The polyps have an outside diameter of about 3/8 - 1/4".

2) The coral is located at the bottom of my rockwork, away from any other potentially threatening corals. I have never observed, either during light-on or light-off periods, any fish or inverts harassing this coral. The flow in this region is moderate.

3) About 10 - 20 min after feeding the tank, the interior of the polyps will swell slightly, and the tips of the tentacles (about 1/2 mm) will extend into the interior space of the polyp, looking like the circular ring of teeth of a lamprey, for example. When the polyps are so extended, I can squirt mysid shrimp into the polyp cavity, and some will stick to the tentacle tips, leading to a rapid engulfment of the food particle. Unfortunately, this feeding routine is hit-or-miss, working only about half the time.

[EricHugo]

1. no
2. doubtful, and if possible, highly abnormal for the coral