carbon use and alkalinity

[Jasontkd]

Hey all, a little background to my question:

I have a 40 gallon breader SPS dominant tank, with a 20 gallon sump. I have some LPS and zoas, and i run carbon 24/7. Everything has been doing pretty well for about a year and my alk was consistantly between 9-10. Anyhow, the powerhead on my carbon reactor started making a lot of noise, and needed a new impeller. So anyhow, I ordered one and got it in about a week.


So, for a week i wasn't running carbon. I noticed some of my SPS looking a little weird, they had some of the acro tips were browned and I didn't have a lot od polyp extension.

I started testing my water, and my ALk was up to 14.5

does carbon cut the alk in the water column? or is there some other issue that caused this spike?

 

[MCsaxmaster]

After rinsing, activated carbon shouldn't measurable impact tank alkalinity. What may be the case is that without the removal of nasty organics by the activated carbon, the corals were somewhat stressed and growing slower. With the same alkalinity supplementation but lower demand, alkalinity rose over time.

Of course, without actually testing those ideas out, it's impossible to say exactly what happened.

 

[tmz]

<a href=showthread.php?s=&postid=13146264#post13146264 target=_blank>Originally posted</a> by MCsaxmaster
After rinsing, activated carbon shouldn't measurable impact tank alkalinity. What may be the case is that without the removal of nasty organics by the activated carbon, the corals were somewhat stressed and growing slower. With the same alkalinity supplementation but lower demand, alkalinity rose over time.

Of course, without actually testing those ideas out, it's impossible to say exactly what happened.

Seems like a very likely explaination and now the adverse reacton to the high alkalinity could slow down consumption even more. Is your calcium high as well?Perhaps you should stop dosing for a while?

 

[MCsaxmaster]

<a href=showthread.php?s=&postid=13150776#post13150776 target=_blank>Originally posted</a> by tmz
...the adverse reacton to the high alkalinity could slow down consumption even more.

What adverse reaction? In every species of coral every examined, higher seawater (carbonate) alkalinity (all else equal) yields higher rates of calcification.

 

[tmz]

Yes I understand that but is there a top end limit?Would that hold true for the 14.5dkh alkalinity he noted in this situation for example with the burnt tips?
Or is the notion that high alkalinity in the 14 or 15dkh plus range is harmful to sps a widely held misconception? If so I would like to understand it better since I have seen this type of reaction occur in my tanks if I inadvertantly allow the dkh to rise into the teens. My reaction is to stop dosing when this occurs and to slowly reduce it. Should I be looking for an external variable ?. How high can it go before it does harm all things being equal? Thanks for your help.