Low alk causing some coral bleaching?

[slapshot]

I completely agree with the above points. Athough there is no documented problems with high Alk until you hit the point where calcium comes out of solution. I run my Alk at 12 sometimes 13 because it can drop to 3 points in a day when all my SPS are growing. The precip point is somewhere north of 15. I believe a lot of the problems with SPS in peoples tanks are they run their alk to low and the the swing down to the point where they can not use the calcium. 8 or 9 in the ocean is fine but in a closed system it can change too fast.

 

[slapshot]

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[JER-Z]

rich do you have any pics of your corals w/ these bi-daily alk swings?

in my tank i noticed the tighter i can keep my alk, the better colors i get. Some are more tolerant to swings than others, but what you claim goes against everything i have experienced. I've had some smaller non-lethal swings like you describe and stuff has gone pale overnight.

 

[airinhere]

I recently went into the Chemistry Forum asking specifically about the impact of low dKH values in our reef tanks. I tried asking outright, using illustrative examples and most importantly, being persistant. The response I recieved is that unless the dKH is at wildly low (or high) levels, it can not do anything directly in our tanks. At very low levels it can interfere with calcium uptake and cause reduced growth. The biggest risk is the ph shift that becomes possible when the dKH is very low.
Heres the link to the thread I started.
http://reefcentral.com/forums/showthread.php?s=&threadid=1143667
I am very inteested in making sure I have the most accurate information regarding this topic, so if anyone has anything to add to my old thread, please chime in there and lets drag boomer or Bertoni in so they can help clear this up.

 

[airinhere]

RichConley

'PH on the open reef can swing a full point in a couple hours.'

I thought the ocean was extremely stable as far as ph was concerned. As in barely any difference anywhere.

'The issue isnt PH, its the Alk itself.'

Alk allowed to lower to certain levels has a huge impact on pH.

'Corals/Saltwater invertebrates dont perform photosynthesis the same way freshwater stuff does. Freshwater organisms use dissolved CO2 for carbon, corals dont. They use the carbon from bicarbonate (alk!). So low Alk means they can't photosynthesize, and are starving.'

Corals dont perform photosynthesis at all. The zooxanthelane(sp?) do perform photosynthesis. And they use CO2 to do this just like all other plants and algaes.

The corals use the carbonate from alk to bind to the calcium dosed into our tanks to form calcium carbonate and that is what the skeletons of corals is made of.

Corals (SPS) feed on zooplankton. They get additional nutrients from the wast products of their zooxanthelane, but it is not their only source of food.

'This stability thing is such a crock. I can swing from 8-11 dkH twice a day and not lose anything. If I hit 6.5, or 13, I lose stuff. Thats not a stability issue, thats being outside acceptable parameters.'

Stability is critical to any corals long term success. 8-11 dKH is in the acceptable range for dKH values and you should not see any negative impact as long as your readings stay in this range. Get much lower than 8dKH and you risk having wild pH shifts in your tank. The lower pH (increased amount of acid) is potentially fatal to any coral. Get above 11dKH and you wold really have to overdose to hurt your corals. Usually the damage is from the increase in ph over a short period of time (shock them).

I am only jumping into this because I run into lots of people at work who suffer issues just like we are debating here. If I am wrong on anything, correct me now before I tell someone something that is wrong.

And Rich, I do not want you to feel like I am ripping on you. I just am concerned that after a thread goes this long without making any headway, anything that can seem like it is factual should be reviewed and critiqued before other people (like me) start using it as the basis for our reefing knowledge.

 

[RichConley]

If you really believe the ocean is stable, read this

http://www.reefland.com/rho/1105/reefc7.php

And yes, you are technically correct in that "Zooxanthelle perform photosynthesis, and use CO2", but are incorrect with the larger picture. Zooxanthelle gain their CO2 from the coral they inhabit, and that corals strips the CO2 from bicarbonate, aka Alk.

 

[airinhere]

That article says nothing about the pH of seawater. It says that the ocean has varying temperatures (which I hope we all know about) and it says that salinity can shift especially where fresh water is released into it or when it rains. (But mostly in the top 20 m.)

When I say the ocean is stable, I am refering to its chemical and trace element composition. It is obviously going to have varying amounts of silt or other stuff in it, but the core elements of ocean water remain very constant over large expanses. This is why water from Catalina was used with success for tropical reef tanks even though Catalinas water is in the 50F or colder range and no tropical organisms could ever survive in the Pacific northwest .

So you are saying the corals are a source of CO2 for the zooxanthela? I thought the zooxanthela got the CO2 from the water as it respirated and then the waste products of the zooxanthelane were utilized by the coral for some of its nutritional intake. (simple sugars and amino acids.)

As far as Bicarbonate being utilized by corals, I was under the idea that the corals tilized the bicarbonate only to help bond the calcium, magnesium and strontium they gathered from the water column to help build their skeletons. As far as I understand, the bicarbonate does not play a significant role in any other method than just skeletal development for the corals.

Time to do some reading. Any suggestions on sources for the bicarb usage you might recommend?

 

[airinhere]

found this about bicarb uptake.

http://reefkeeping.com/issues/2006-10/rhf/index.php

I had no idea about this and am glad you pointed it out.
The summary at the end, covers the basic ideas.

 

[Grandlotus]

RichConley

'PH on the open reef can swing a full point in a couple hours.'

I thought the ocean was extremely stable as far as ph was concerned. As in barely any difference anywhere.

'The issue isnt PH, its the Alk itself.'

Alk allowed to lower to certain levels has a huge impact on pH.

'Corals/Saltwater invertebrates dont perform photosynthesis the same way freshwater stuff does. Freshwater organisms use dissolved CO2 for carbon, corals dont. They use the carbon from bicarbonate (alk!). So low Alk means they can't photosynthesize, and are starving.'

Corals dont perform photosynthesis at all. The zooxanthelane(sp?) do perform photosynthesis. And they use CO2 to do this just like all other plants and algaes.

The corals use the carbonate from alk to bind to the calcium dosed into our tanks to form calcium carbonate and that is what the skeletons of corals is made of.

Corals (SPS) feed on zooplankton. They get additional nutrients from the wast products of their zooxanthelane, but it is not their only source of food.

'This stability thing is such a crock. I can swing from 8-11 dkH twice a day and not lose anything. If I hit 6.5, or 13, I lose stuff. Thats not a stability issue, thats being outside acceptable parameters.'

Stability is critical to any corals long term success. 8-11 dKH is in the acceptable range for dKH values and you should not see any negative impact as long as your readings stay in this range. Get much lower than 8dKH and you risk having wild pH shifts in your tank. The lower pH (increased amount of acid) is potentially fatal to any coral. Get above 11dKH and you wold really have to overdose to hurt your corals. Usually the damage is from the increase in ph over a short period of time (shock them).

I am only jumping into this because I run into lots of people at work who suffer issues just like we are debating here. If I am wrong on anything, correct me now before I tell someone something that is wrong.

And Rich, I do not want you to feel like I am ripping on you. I just am concerned that after a thread goes this long without making any headway, anything that can seem like it is factual should be reviewed and critiqued before other people (like me) start using it as the basis for our reefing knowledge.

Thank you very much!!