Why did my Alk stop decreasing?
 

About a 10 days ago I had a 1.8dKH jump in Alk over 48hours. A BRS dosing pump malfunctioned (my fault for not changing the tubing), Alk jumped from 7.5dKH to 9.3dKH. Since then I have suspended WC's and stopped dosing in order to reduce levels back to around 7.5dKH. However, in the past 10 days my Alk has remained high at 8.9dKH.

What is going on?!?!

Previous to this I was dosing approx. 14ml daily of Randy's Recipe #1 and my parameters were stable.

The only change I made was to start dosing ZeoBak and KZ Sponge Power just before the Alk spike. But I don't see how that would contribute to Alk not falling in 10 days.

Other than losing my favourite Acro during the initial spike, all the inhabitants look happy. Aside from a few burnt tips, colouration of my remaining SPS never been deeper.

My thoughts:

1) Dosers were previously failing and I've been overdosing 2 part this whole time. Though I don't think this is likely as parameters had been stable.

2) The alk jump was severe enough to shock the corals and they are still recovering before growth and Alk consumption resumes.

3) N03 and P04 have dropped. Could the bacteria from the ZeoBak be consuming N03 with P04 and in the process producing Alk?

So confused.....:hmm3:

System info:

60 gallon (net volume) with sump.
10l Siporax
50ml Rowaphos in a fluidized reactor
Vertex 150 skimmer

Here is a history of my test results:

September 18, 2017 - Started dosing ZeoBak & KZ Sponge Power
Sg = 1.026
T = 79.5
KH =7.5dKH
N03 = 5ppm

September 20, 2017
Sg = 1.026
T = 79.1
KH =8.6dKH

September 21, 2017 - Took dosers offline
Sg = 1.0265
T = 79.5
KH =9.3dKH

September 22, 2017
Sg = 1.026
T = 79.5
KH =8.9dKH
Ca =460ppm
N03 = 5ppm

September 23, 2017
Sg = 1.026
T = 79.5
KH =8.9dKH

September 24, 2017
Sg = 1.026
T = 79.5
KH =8.9dKH
Ca =460ppm
N03 = 5ppm

September 27, 2017
Sg = 1.026
T = 79.5
KH =8.9dKH
Ca =460ppm
N03 = 2.5ppm
P04 = 0.009ppm

I would say its option 2.

I agree that the corals might be recovering still. Generally, there's not enough added alkalinity from denitrification or carbon dosing to make much of a difference. How much has the nitrate level dropped?

Nitrate has dropped about 2.5ppm.


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#2 gets my vote also..

That nitrate drop won't make a significant change in alkalinity:

http://reefkeeping.com/issues/2004-12/rhf/index.htm

About 0.03 meq/L, I think.

Thanks for the replies. Alk consumption has finally resumed although the burnt tips are quite bad.


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