No polyp extension...a good thing?

[Anonymous]

My neon green tree coral never extends it's polyps out fully. It will contract at night, and then unfurl toward the light, but doesn't look 'fuzzy' with polyps extended. it's about halfway up in my tank, and I have 440watts of VHO lighting. Should I move it down, or do the absence of polyps indicate that it's being satisfied? Any help is appreciated...

Peace,

Chip

 

[Goldmoon]

They must be like any other leathers..
My guess is yours is a new addition? If so, give it a chance, sometimes it can take up to two weeks before they fully open. They also like current. When they close up like that there is a light skin that covers them (usually glossy but if it stays like that for a long period of times it might be covered with algae). The current helps remove the skin when it is ready to re-open.
They will do that repeatedly as they grow.. you will notice that after it does that for a few days, they open up bigger and nicer afterwards.
I have one like yours, (at least I think it is the same) and it took at least 4 days before it opened up its polyps. Now when it does it turns yellow.. and at night or when polyps are closed it is green.. strange..
good luck with it.. they are nice corals

 

[jamesw]

[let me edit this post along the lines of what Chucker mentions below]

Well, this looks like a good opportunity to "debunk" one of the biggest myths about corals in aquaria.

Corals aren't really "supposed" to extend their polyps during the day.

In the wild, corals DO NOT extend their polyps during the day, for 3 reasons:

1) A butterfly or some other fish will come by and eat them.

2) Polyps are primarily for feeding and that means catching things. Most things that corals eat (like zooplankton) is out on the reef at NIGHT, not during the day.

3) Corals extend their polyps to expose more zoox. to the light. That's because they are not happy with the amount of light they are getting, and want more exposure.

This pretty much applies to hard corals and not soft corals. Soft corals are pretty "untasty" and they make themselves that way so that fish won't eat them. Soft corals do extend their polyps during the day.

So, this doesn't really answer your question about your specific coral I realize, but I think it's good information for everyone. Take a look at your tank at night and compare it to the daytime extension, then let us know what you find.

HTH
James Wiseman

[ October 03, 2001: Message edited by: jamesw ]

 

[Chucker]

I'd add a caution to that statement. Polyp extension in some cases is desirable. It can be very useful to gauge coral health after shipping, fragging, or any other traumatic experience for the critter. In those cases, it's a visible response that the coral is reacting to its environment again.

The other caveat I'd add (one that james just clarified in the #reefs chat channel) is that the rules he listed don't alway apply to soft corals, since many of them are relatively poisonous to fish.