Hi, jadavis01
Darkening in corals and polyps usually indicates an attempt to better utilize available light, as in, there is less light than it is used to, so it increases the active pigment in the photosynthetic 'zooxanthellae' it hosts, and their numbers. The brown pigment in these beasties can darken polyps.
On the other hand, polyps may turn dark in joyous exploitation of a return to "correct" lighting (after having gone pale in darkened transport containers, holding tanks, or even niche locations in the wild).
I'd wager it's the lattest case, if only because
P. gracilis is notorious for it (I think Eric B. mentioned this a few times, years ago). You can try moving it slowly down to the bottom of the water column, in partial shade, even.
If it darkens further, then you know to move it further up than originally (but gradually). It will take quite some time to determine its response, so go slow.
The possibility that it is boosting zooxanthellar productivity because it's not getting enough ingested nutrition is unlikely if you're already getting it to feed successfully.
Now, if this is one of those unusual cases where the polyps have dumped one sort of zooxanthellae for a more efficient kind (with a different shade) --again to suit new lighting conditions, then we may have difficulty getting the polyps to exhibit their original hue.
hth.
horge
[ 04-05-2001: Message edited by:
dark horge ]
