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Rising Calc - High-ish Mag in new system

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Hello - My tank has been running since Sept 19th so it is fairly new and I am thinking that what I am seeing from my parameters is due to such a new system.  I only started to test my Alk/Cal/Mag on the 9th of Nov.  The last water change I did was just over a week ago.  All of my parameters are in a decent place(see below) and the Mag seems to be coming down on it's own.  I am slightly concerned on the Alk and Calcium, I know as Alk goes down Calc will rise.  I was planning on holding off on a water change until the two week mark as that is where I'd like to be.  


Test Date  Ammonia  Nitrate  Phosphate  PH  Salinity  Alkalinity  Calcium  Magnesium
Nov 22, 2020 0 ppm 10 ppm .03 ppm 7.9 35 Parts Per Thousand 8.3 dKH 490 ppm 1530 ppm
Nov 9, 2020 0 ppm 10 ppm .05 ppm 7.8

35 Parts Per Thousand

8.9 dKH 440 ppm 1850 ppm


My livestock consists of a single clown, a blasto with one head, a few mushrooms, candy canes, small favia frag, finger and toadstool leather, kenya tree, a few zoa frags, hammer and a goniopora.

I feed 3-4 times a week and broadcast a small amount of reef-roids once or twice.  The clown has stopped eating flake and pellets and will only eat frozen.  


Everything looks to be doing well.  Should I do a water change or hold off until the two weeks is up?  Is there any concern for the calc rising/alk droping or is this on par for a new tank?  I wouldn't think with the LPS I have it would be consuming that much Alk, but I've definitely been wrong before!




I use Fritz RPM and it should be mixing at

Salinity: 35 ppt


8.0-9.0 dKH

Calcium: 400-450 ppm

Magnesium: 1300-1400 ppm 

- I have not tested a batch of new SW yet, but plan to this evening as I have a batch mixing.  




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3 hours ago, afrostyreefer said:

I have not tested a batch of new SW yet, but plan to this evening as I have a batch mixing. 

When you do test it, note down the results. Then aim for those levels regularly. 


How are you testing magnesium? Which test kit?

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Magnesium being high is not known to cause issues but if it is below normal levels, that's when it can become a problem.


Your levels looks fine for a new system. Rock and sand will also use up some ca and alk.


Definitely recommend testing new sw so you know the target levels and when you do a waterchange, test the alk, ca, and mag about an hr after just to see where the tank is at.

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