Thoughts on SPS polyp extension..

Aquattro · #1 08-04-2011, 04:46 AM

What causes polyp extension in SPS, or rather, what causes polyp retraction? I noticed a few months ago that about half my colonies no longer have noticeable extension, day or night. Others are fine, although not what they once were.
I think it started with a change in salt, but returning to my original salt hasn't restored the PE...

Thoughts??

BlueTang<3 · #2 08-04-2011, 04:49 AM

potassium?

Aquattro · #3 08-04-2011, 04:53 AM

Quote:

Originally Posted by BlueTang<3

potassium?

how so? Not something I've ever tested

And if so, why great PE for a while, but not now? I do 40% water changes bi-weekly.

Aquattro · #4 08-04-2011, 05:00 AM

And something else to think about...should there be any daytime PE in the first place? Corals in the wild tend to not extend other than at night (from what I've read). so is something missing in our tanks that they're trying to get? does that mean my tank is supplying it? I have a lot of light, perhaps they get enough from photosynthesis?
So is daytime PE good or bad?

lastlight · #5 08-04-2011, 05:02 AM

Good question. Has it ever been shown to be a good sign to have massive PE? I know I like how it looks but I'm curious to hear if anyone knows more about this.

I will say that I never see corals on their way our with great PE.

Aquattro · #6 08-04-2011, 05:09 AM

Quote:

Originally Posted by lastlight

I will say that I never see corals on their way our with great PE.

Agreed, although none of mine are on their way out either. Growing well, good color, etc, just not the PE they used to have. I even have a milli that is barely extending!

marie · #7 08-04-2011, 05:48 AM

I could be wrong but one of the reason for lack of extension in corals in the wild is predation. My acropora don't extend their polyps much during the day because I have 4 angels that constantly nip at them and I suspect my copperband butterfly also has a taste now and then

Aquattro · #8 08-04-2011, 05:52 AM

Marie, I thought about that, but really can't see any fish nipping, and I've watched for hours straight. And I had strong PE with these fish, it just stopped after switching salts.

lastlight · #9 08-04-2011, 05:56 AM

Maybe the substrate in your water column is sand-blasting them =)

PoonTang · #10 08-04-2011, 06:01 AM

I had the same problem. Fought it for months and months and tried everything from additives to new salts to massive water changes. It turned out to be a tiny little yellow coral goby whom I had never ever seen nip at a coral. But within a week of him being moved to the nano tank my polyps came back.