Low dkh and high calcium, magnesium

[Bcountry]

Today i tested my tank to find the following readings:

dkh - 5.6
mag - 1600
cal - 500
pH - 7.8


This is a 120 gal tank with a sump, im running purigen, phosban in media bag and activated carbon.

Im trying to understand how to get these under control and back to normal.

 

[Tahoe61]

I would double check the dkh value. What test kit are you using?
Have you been dosing at all and what?

 

[Pete polyp]

With your calcium that high more than likely you have precipitation. This will help...

http://www.advancedaquarist.com/2002/11/chemistry

 

[saltyfish]

Are you dosing anything in the tank or using a calcium reactor? Your magnesium levels are pretty high also. What is your salinity and what are you using to measure it? What salt are you using?

 

[howaboutme]

I had this exact issue recently. My #'s were almost exactly the same except my alk got to 5 and my calc was a bit higher than yours (zone 4 in the article linked) but I was not dosing anything. My hypothesis is that as my tank slowly became sps dominant, my tank was consuming Alk at a much higher rate and water changes did not keep up. Alternatively, my water changes did keep up w/ consumption. I also almost never test my tank so I was not spotting a trend. Tank looked great visually, which is why I was never concerned.

I fixed the issue by slowly bringing up my alk (about 1dkh/day), first to 7 and then to 8 over the course of a week or so. Then at this level, as alk is consumed, your calc will balance out eventually. Now I only dose alk to maintain. Don't get too caught up on your Mag and Calc #'s. When you get your Alk in check, those will fall into place as a result.

 

[Bcountry]

My salinity is 1.023 using a refractometer, I have my tank set at 77 degrees and I use reef crystals. I dont dose anything because my numbers are usually in check.

 

[saltyfish]

What corals do you have in the tank? You may need to supplement the alkalinity if it is being used up too quickly.

 

[backpack]

If one is low the other goes up. Kind of like a sea saw. Think of mag as the fulcrum in the center.

 

[Bcountry]

I have the following coral:
-pulsing xenia
-eagle eye zoa
-trumpet (candy cane)
-goniopora
-green star polyp
------Fish-------
longnose butterfly fish
2 occelaris clowns
yellow clown goby
very small juvenile blue hippo tang

 

[Pete polyp]

I have the following coral:
-pulsing xenia
-eagle eye zoa
-trumpet (candy cane)
-goniopora
-green star polyp
------Fish-------
longnose butterfly fish
2 occelaris clowns
yellow clown goby
very small juvenile blue hippo tang

The candy cane and goniopora both use calcium and alkalinity to build skeleton.

 

[ws6kid]

I think I read that the dkh being higher, around NSW, will allow animals to absorb the calcium more readily which balances the numbers out. Definitely need to keep dkh around 7 minimally. If you aren't interested in dosing, you can just find a salt mix that has a higher alk content so it will be replenished more with water changes. ESV 2 part makes it easy to just add what you need.