Polyp Extensiuon - Rumor or Fact?

[Hookup]

I've picked up this 'rumor' on my travels and want to see if it is grounded on fact or just some thread-rhetoric.

Often times polyp extension is a coral attempt at controlling water flow. If a coral would like less flow, it would extend its polyps to create turbulence and effectively slow down the flow around them. If they want more flow, they do not extend their polyps creating a more "slippery" surface for water to move by quickly

While I can see how this would not necessarily be a "hard rule" but I can see some logic behind the statement.

The question remains, is there any validity to the entire concept or is this just pure rumor?

 

[maharsreef]

If thats the case, I guess all my sps want less flow! lol's I think it's bs. But what do I know?

 

[Ephraim]

i would think the opposite. Extending the polyps more during high flow conditions would cause more physical stress to the polyps.

 

[Puffer Chick]

im still new to corals especially sps but i have noticed the difference of my birdnest polyp extension in high and low flow areas.

When i first placed my birdsnest close to my vortech mp20 it had no polyp extension what so ever, but as soon as i moved it to the other end of the tank, it has some beautiful polyp extension going on, so that kind of let me know that it's happier where there is less flow

not sure if this helps at all, just my experience

 

[t4zalews]

my saying is if you have polyp extension then the coral is happy. I've found that if in too much flow..sps will not extend polyps as usual.

 

[arioch]

Sure if you put it right in front of a powerhead or whatever, it's not going to be able to extend polyps and in fact the flesh will probably just start peeling off the skeleton ...

But if I could venture to ascribe an emotion to a colonial organism it would be "happy" when my sps pieces are sitting in the middle of a pair of powerheads set to "wavemaker".

 

[MAMGM]

I would say polyp extension has more to do with lighting than flow

 

[elijaher]

Some reefer has polyp extension only during night.

 

[cato]

my saying is if you have polyp extension then the coral is happy. I've found that if in too much flow..sps will not extend polyps as usual.

+1 ^^^

 

[luther1200]

I agree. The only time I've ever noticed polyps retracting is from to much flow. If a SPS tried to extend its polyps during a Typhoon or something to slow down the water they would be ripped right off I would think.

Another way to test would be to point a PH or something at a SPS. And in theory it should extend its polyps if this were true. When if fact they will do just the opposite.

 

[Hookup]

LOL... yes, I agree... in extreme circumstances there's no hope that any amount of extension will save flesh from the direct force of a powerhead or a typhoon... lol...

I do wonder, does everyone have good extension on all of their pieces in their systems or only some?

 

[preef]

I one of my PH was accidentally pointed at a digitata branch. Ther was no polyp extension ant all on that branch. It was so bad that after only a couple days algae was growing on it. I redirected the PH and the next day the polyps were back and the algae was gone.

 

[Amphiprion]

They can alter fluid dynamics on a macroscopic scale, which will also change the effective thickness of the boundary layer around them. Basically, they can tailor the flow around them to a certain degree to better fit their needs at that point in time. In the end, it is only a matter of increasing or decreasing surface area, which can be done for number of reasons--not just flow.

Oh, and I stumbled across this as I was typing. It says what I said, albeit more eloquently and in much more detail: http://www.advancedaquarist.com/2006/11/aafeature

 

[Kataro]

wow! epic physics to be applied to this hobby lol.

 

[29reef]

The polyp is how the coral catches it's food and gets rid of waste. I don't think you can relate water flow and the amount of PE. Generally PE has to do with the time of day and what is in the water colum.