Thoughts on SPS polyp extension..
 

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??

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.

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?

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.

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!

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

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.

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

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.

Ya, that's my original thought, irritation from the turbidity. I swear I'm losing 30% of my light to the dust cloud!

Darren, pretty sure it's not fish, I have mostly large tangs and a couple of large wrasses, 4 clowns. No known coral nippers.

Polyp extention
 

I had massive extention in most of my Sps colonies for a long time and then they just stopped! I tried every thing and finaly narrowed it down to a small voltage leak. I spent 14 bucks on a Rid Volt and within hours the extention was back!
It could be different problem for you but only $14 dollars out of pocket to try.
Keith.

Keith, not a bad idea. I just browsed the tank and noticed that some pieces do have good PE, especially a newly mounted pink lemonade. Pocci colonies all have great extension, as do the birdnests. But some colonies have nothing at all. For 14 bucks, I'll try grounding the tank.

Interested to hear the result of that.. Tagging along.

Haven't seen a whole lot of reefs in the wild but the ones I have seen, have all been in the daytime, and I don't ever remember thinking "Boy the polyp extension on these acros is not very good. I wonder if it's better at night time." Everything I've ever seen has all had PE to some degree, acros, porites, etc and eieio, but that said I've never seen the shagginess of a typical prostata or milli. So whether that's because maybe I never saw a prostata or milli where I've been, or if that's just not a natural occurrence, I can't say..

Tony, the wild milliporas I've seen didn't appear to be super fuzzy like we see them in tanks, if I recall. I wasn't paying a lot of attention to PE, more the size of some of the wild colonies!

But in my tank, for instance, my abrolhosensis isn't the typical bushy stick you normally see, you can actually see the body of the coral. The first three months, you couldn't tell if it was one branch or three!
The grounding probe idea has merit, and they're 12 bucks locally. I'll try that tomorrow.

The reason i think its potassium is after i dose k balance in the tank the pe is wild might be similar to after feeding the tank tho and the corals are just trying to absorb as much as possible.

do you feed any kinds of coral type food?

Hmm, might give that a try.

No, I feed the fish heavily and figure that's enough.

I've always wondered about this too, particularly in regards potassium dosing and PE. I've always been suspect that K makes the polyps extend by a physiological response rather than their own natural accord as potassium, for most animals, regulates muscle responses and fluid pressure balances between tissues. So dosing K might just be causing them to puff up like balloons... but really I don't know that for sure, so at this point I'm talking out of my a$$.

As for some colonies having PE and some not... I am suspecting an irritant, though figuring out what that may be could take forever. I'd venture to say it's probably sand that is bothering them.

Since I've been curious about this as well, I tell ya what... I've got some time to kill today while waiting for an experiment to finish. I'll dig into some journal articles and see if I can't get some sort of definitive answer.

That would be great. I too suspect the sand, it's really turbid. I picked up a grounding probe and some K, I'll see what that does later this afternoon. I found a way to get the sand out, so that's the next step.

You've got your significant other working the 5g buckets? Tsk tsk!

Bwahaha....

step 1) show s/o photo of bobbit worm
step 2) tell them the last person you got frags from (insert name) has just discovered one in their tank
step3) tell s/o there are most likely eggs in your sand bed that will hatch in about a week.
step 4) in a few days admire your spotless tank with the nekkid bottom.

insert beer where required.

Ok, so this is what I've got so far...

All corals have some mechanism to remove sediment and debris from their surfaces. Larger polyps exhibit 'twitching' mechanisms, whereas small polyped corals tend to have a full retraction of the polyp, leaving a relatively smooth skeletal surface which currents can easily blow sediment off of. This same response is also triggered by irritants like little red bugs so, if your polyps are continually not opening, it is most likely the turbidity of your water. Though it makes me wonder because my turbidity is also pretty high and my polyps couldn't be hanging out any further. No little bugs or AEFW?

I also found that corals with poor health (for various reasons) would tend to not extend their polyps.

But this is all stuff we kinda already knew....

In terms of potassium, corals definitely have a response to it as noted by several researchers but no one has really offered a difinitive answer on the matter. I did find that potassium DOES regulate pressures within coral membranes but I can't actually say that is what is causing the polyp extension. The explaination offered by a number of researchers that K is a limiting nutrient and that corals exhinited better health on its addition. They observed (cut and paste directly from the document):

- better growth of all photosynthetic organisms,
- more polyps at SPS,
- intensified branching of SPS,
- less „asthenic“ growth of branching SPS,
- intensified colors of colored corals,
- often a higher demand of macronutrients, due
to the increased primary production.

Unfortunately, no one knows why yet...

My watchman frequently puts plenty of fines into the water column and I also have great PE. I was originally kidding about the sand but under the right circumstances who knows?

no sandbed here but my fish crap a lot so I might as well call it turbidity :razz: PE has always been good (especially with the wavebox) and I had no PE when I had a sandbed (granted, PE was the least of my problems when I had a sandbed). I found when I dosed K I got better colors but I don't remember getting any better PE than without dosing. I'm thinking about taking up dosing again just to see if it does anything.

Just added the grounding probe and some K. We'll see what that does. If I get better colors, I suppose I'll have to live with it :P

The water column is actually pretty turbid, to the point you can see a solid beam of light from my PFO reflector. I can well imagine that the suspended particulate could irritate the corals.
The sand has to go anyway (I've got the use of a large filter to recycle the water), but the probe or K could also do it.

See what i have noticed is the natural direction of the water in the ocean you get the back and forth. In tanks you get all around crazy people think that having all this retarded flow is working. When I was diving in the oceans in the Mediterranean the water isn't at all like what we have in the tanks.

So, a few hours later and I do see some increased PE. Not sure if it was the probe or potassium tho :)
Still not what it was, but I'll give it another day..

:popcorn:

Brad,

take a multi meter and stick it in the tank, mesure if there is voltage (dont put the ground probe in yet.

than do the same with the grownd probe in it, I had it that I had I think it was 4.5V hanging in my tank.

I now use the Zeo K ballance sinds a week, and most of the coral are defenetly more fluffy from the PE

thing Ihave going on now is that about 3 weeks ago, I also lost PE on 50% of my SPS, as well as these same 50% lost collor.

the other 50% are all fine, and sinds dosing the K ballance the PE is way, way better.

maybe there is something in the water locally, that is not filtered out by the RO unit, I replaced all filter cartridges last week, to make shore I have all options delth with.

I will tonight mesure my water voltage again, as now stray voltage is broth up, I think that in deed, something is wrong with my probe, and this could be my reason (I never checked the probe again after I placed it in

polyp extention during the day is not a normal thing. I only had extension at night with all my corals, but for some reason people seam to like it. my theory is that if there extending there looking for food as the polyps are there food catching tools, but who knows, I could be out to lunch also... but from reading I did years and years ago no extension during the day was normal as they are feeding off the light, at night when there is no light or at times when the light isn't enough they will extend to both catch food and increase the surface area exposed to light.

Steve

wild sps dont extend their polyps during the day due to diurnal predators...... nothing to do with available light or food.....I noticed a huge increase in PE when I started with phyto/zoo plankton feeding.....

Polyp extention
 

I run three 400 watt halides over my 6' tank, believe me there is no light shortage. I think the polyps are extended during the daylight due to a lack of predators. Some seem to extend even more during lights out though!
Keith.

Keith, I run the same light, no polyps. Corals are all doing great, just curious why the polyps stopped coming out.

thats what I would get, some extension during the day, at night it was way more.

Steve

It is my understanding that PE is a result of the coral sensing a level of available nutrient in the water. Like for example a Sun Coral and our ability to train it to open. A lot of fish feeding will trigger PE of all corals.
I don't believe sand storms would cause a lack of PE as most wild corals live in very turbulent areas with waves crashing directly on top of them.
It's my belief Potassium could be a trigger that tricks the coral to believe food is available. I also am a believer that Potassium is an important in a reef, but be very careful as over dosing will kill fish

J

I had a potassium shortfall on my tank, I use redsea pro kit to test for potassium. My reading was just under 360, I have since bumped it up to 430 ish with zeovit k balance. I have found it useful looking at the new polyp extension on several of colonies of sps which had no extension before and with brighter blue coloration. I do run pellets on the system, I strongly believe while running a probiotic system potassium gets striped out of the system way too fast, one must replenish it with supplements to ensure sufficient levels are met. Ofcourse with most supplements I don't like to dose anything I can't test.

On a side note. I found feeding also aid polyp extension as it is the reason why there is polyps in the first place.

I am interested in the grounding probe. I guess it's time to stick the good old multimeter in the water and see if there is any stray voltage.

Keep us posted on the progress.:wink:

My sps have full polyp extension 24/7. The only time they retract is when I touch them or when I do water change and they are exposed to air.

I guess my tank must not be normal.

No, it seems sort of normal to be out, depends on the tank. Lots of great tanks have full PE, and lots don't.

For me, adding K has produced a bit more PE, but nothing substantial. I do have perhaps 12 colonies that have full PE, but another 80 that don't. Not sure why.
I added some brine shrimp today to see if that provoked more response, nope. I feed mysis daily, no change. I've just modified my zeo dosing, I may have been adding too much, so perhaps the corals aren't hungry. I have nothing picking at them, so it's not predation.
Levels are all really good and stable. alk is a bit high for a zeo system, so perhaps that affects it, since the water change that seemed to set this off did raise my alk substantially. I'm trying to get it back down to 7dKh and see if that changes anything.
Again, not sure if PE during the day is a good thing or a bad thing, I do have typical PE at night, corals are colored great, and growing well, so I really don't have a problem, but they do look prettier when extended.