BioPellets and Alkalinity in a lps and softy's

[Eric Morissette]

Just curious i have been reading everywhere saying to keep my Alk at 8 with biopellets with SPS coral, do i need to do the same with LPS and Softy’s?

 

[Randy Holmes-Farley Verified Community Expert]

That guideline is somewhat misguided, IMO.

The alk concern has nothing directly to do with the pellets. It has to do with very low nutrient systems. If you use the pellets to drive nitrate very low, then you do not want alkalinity too high or some hard corals (SPS) may get burnt tips, possibly because the skeleton grows faster than the tissue can keep up.

It is not a concern for soft corals (except that very low nitrate may not be optimal for them at any alkalinity) and the alk issue is not improtant for hard corals IF you do not use any method (inlcuding, but not limited to, pellets) to drive nitrate very low.

I've not heard of issues of LPS with low nutrients/high alk, perhaps since they naturally grow more slowly, but I'd be careful.

 

[JonasRoman]

That guideline is somewhat misguided, IMO.

The alk concern has nothing directly to do with the pellets. It has to do with very low nutrient systems. If you use the pellets to drive nitrate very low, then you do not want alkalinity too high or some hard corals (SPS) may get burnt tips, possibly because the skeleton grows faster than the tissue can keep up.

It is not a concern for soft corals (except that very low nitrate may not be optimal for them at any alkalinity) and the alk issue is not improtant for hard corals IF you do not use any method (inlcuding, but not limited to, pellets) to drive nitrate very low.

I've not heard of issues of LPS with low nutrients/high alk, perhaps since they naturally grow more slowly, but I'd be careful.

I must comments one thing here: I do not think it is true that this is due to too fast skeleton growth, I think that is an old explanation not valid. I think, based one some studies concerning this, that the burnt tips is due too the fact that increased alkalinity is increasing the photosynthesis in the zooxanthella, and that is in turn increasing production of free radicals, peroxides etc, which can damage the coral, specially in the distal tip where the photosynthesis is of highest activity.
There are some studies which proves very nice how the photosynthesis of the zooxanthella increases with increased HCO3(as zoox uses HCO3 predominantly as carbon source), thus with increased alkalinity. Same study also shows, and that speaks in same direction, that the photosynthesis increase if you in an experimental setup increase pH without letting it be in equilibrium with air (in the study the had an air/water interface without CO2 in the air, just N2 and O2). In that setup the total amount of DOC is of course constant (CO2+HCO3+CO3) thus only the relationship was altered as the pH was altered with HCl and NaOH respectively. When increased pH in that setup the photosynthesis in the zoox increased, thus indicating that the zoox not only can use HCO3 but also prefer HCO3 instead of CO2!.
Well, all this and some other studies, tells us clearly that the photosynthesis is increased with increased alkalinity, and that over a certain critical point could maybe lead to damage to the coral due to overproduction of radicals. In a low nutrient system the coral is extra sensitive to this as the coral is in somewhat way starving, thus have more difficult to produce protective mechanism against these peroxides and radicals.
I also believe, based on the fact that increased HCO3 gives more photosynthesis in the zoox, that our plague dinoflagellates could be triggered by too high levels of dKH. I have seen that a lot of times empirical, even if it may also be dinos with lower dKH. Maybe it is just the increase which is worst, before everything is stabilizing.

/Jonas Roman
https://www.researchgate.net/profil...icarbonate/links/547baa0f0cf293e2da2d737a.pdf

 

[Randy Holmes-Farley Verified Community Expert]

That explanation may very well be true, but the experiments you suggest cannot distinguish the effects from skeletal growth and too rapid of photosynthesis since every experimental variable you mentioned moves them both in the same direction.

That said, if it is excessive photosynthesis, why doesn't it happen in any organism except hard corals? Why doesn't it happen with more light?

 

[JonasRoman]

That explanation may very well be true, but the experiments you suggest cannot distinguish the effects from skeletal growth and too rapid of photosynthesis since every experimental variable you mentioned moves them both in the same direction.

That said, if it is excessive photosynthesis, why doesn't it happen in any organism except hard corals? Why doesn't it happen with more light?

But It think could actually happen with more light of same reason. Therefore it is suggested (by some) in case of too high dKH to temporary decrease light. I think that just that tip burning is less likely if you simultaneously decrease light.
Another reason pointing that there is maybe not the sceleton growth, is that in fact in a low nutrition system we generaly have quite low growth(sceleton growth also) due to starvation. We know for instance how coral growth is increasing with increased nitrat(also sceleton growth) ( to a certain point).
Another aspect again maybe pointing that sceleton growth theory is doubtful, is that this burned tip could come from one day to another. With that speed , thus within 24 h, I doubt you can see coral sceleton building so the tip is naked.

 

[JonasRoman]

One more comment on you last comment: the reason of why this does only happens in sps I think(I do not know of course) is maybe due to the fact that lps have more tissue all the way, so the zooxanthelle in lps and softcoral is more shadowed from the light and thus have a much higher treshold concerning light and dKH before getting too much photosynthesis. But also these corals can come to that stage and may as protection expell their zoox. I think it is not so uncommon to see that especially in low nutrient system.

 

[Randy Holmes-Farley Verified Community Expert]

Well, that could certainly be the explanation. I never had any reasonable explanation for burnt tips until Charles Delbeek suggested the skeletal growth hypothesis, and I usually clarify that it is just a hypothesis.

 

[JonasRoman]

Well, that could certainly be the explanation. I never had any reasonable explanation for burnt tips until Charles Delbeek suggested the skeletal growth hypothesis, and I usually clarify that it is just a hypothesis.

Yes, and so are also the photosynthesis pathway, a hypothesis. Interesting subject

Maybe a subject for a new thread ?