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Discussion Starter · #1 ·
Since addding a Ca reactor a few months ago my Ca/alk has been very stable. Now thw weird thing is my Alk is droping but not my Ca.

What is causing this?

I thought Alk/Ca worked together. 20meg/l of Ca for every 1meg/l of Alk....

So how can by Alk be droping and not the Ca?
 

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spaceman spiff
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Well, that's true for calcification (the 20/1 ratio), but other things take place in the tank. I'm dangerously stepping outside my area of understanding, but as I've heard it alkalinity is the largest source of carbon in the tank. And with bacteria being probably the largest carbon user, I'd start looking at something in that relationship for an answer.
 

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have you tested your Magnesium levels? a deficiency in Mag. will cause these symptoms. you want your Mag to be in the 1300-1400 range. I'd start there and see if things improve.
 

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Discussion Starter · #4 ·
Mag is ok at 1200

I am having a mild cyano outbreak. I got stupid and added some selcon for a few days.

need to do some heavy WC this week and fire up the posban...
 

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Yeah is a SSB only about 1.5"
Alkalinity can be consumed by photoautotrophic bacteria as well as some algae and many facultative anaerobes (they go both ways depending on relative levels of O2 in the environment) as they use alkalinity as an inorganic carbon source in addition to alkalinity's buffer function loses that result from the neutralization of bacteria-sourced organic acids and protons released during bacterial respirations. This can consume quite a bit of your system's alkalinity, so that you can almost always expect to have to either do regular water changes or supplement alkalinity in systems with sand beds (the deeper the sand bed is, the more likely this can become an issue). The use of IO ASW mix is recommended in these systems due to the extra alkalinity provided by this formulation, but unless you do regular water changes, you will be just putting off the inevitable need for supplementation.

Using kalkwasser or a CO2-based calcium reactor will help, but still think of siphoning out detritus and performing water changes to remove organics and left over foodstuffs before they have a chance to decompose is the best answer.

HTH.
 

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spaceman spiff
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that was a bit over my head, can anyone break it down a bit for me ?
essentially, calcification is not the only reason your alkalinity will drop. Bacteria in the tank will utilize it, at times at a surprising rate, depending on the tank setup. A deep sand bed will house more bacteria, which is why it can have more of an impact. As a result of this, balancing alkalinity and calcium in the tank (which is essential for calcifying corals that we're trying to keep) can be more complicated than expected.
 

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Just send me a PM ;)
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LOL... you'll get use to it after a while. Tom's posts were often over my head in the beginning. The more I learned about Reef Chemistry the more I began to understand all those long worded (and often winded ;)) posts of Tom's..LOL
 
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