How much mag do you have to dose?

[Crush Coral]

So I have been working on getting my Mag, Cal and Alk right. This has always been a battle for me. My tank is a 75 with a good hob skimmer so no sump yet. It is looking like I will have to dose about 20 ml/day of Kent Mag. Does this sound like a lot?

 

[Uncle Salty 05]

It depends on what your current level is. Do not dose unless you know. You may not need it.
If you do just follow the instructions on the label and you will be fine.

 

[bertoni]

So it's a 75g system. How much alkalinity and calcium are going into the system each day?

 

[Crush Coral]

I am adding about 100ml of cal and alk. My alk is a little over 8 dkh and my cal is around 300 and coming up.

 

[bertoni]

I'd dose the calcium up about 50 ppm per day. This calculator might help:

http://reef.diesyst.com/chemcalc/chemcalc.html

Once the calcium is in line, the magnesium level should be much lower than that, although it's hard to be sure of the consumption rate, given the accuracy of our test kits. The very low calcium level might (or might not) be encouraging the consumption of magnesium, which can be used in placed of calcium by stony corals and coralline algae.

 

[Crush Coral]

Interesting. I will watch close as I get my cal up too. Thanks.

 

[reef_doug]

You don't mention what your Mg level is? Do you have a kit?

Agree the Ca is low, what is your salinity?

 

[Crush Coral]

My mag is at 1300 now, salainity is 1.025. Now I have to figure out how much to dose each day to keep levels right.

 

[reef_doug]

Unlike for alkalinity that requires daily dosing, Mg depletes rather slowly. Once a month dosing is fine. Assuming you loose 20 ppm per month, your dosing amount would be 4 oz monthly.

1280 - 1300 ppm is a good target.

http://reef.diesyst.com/flashcalc/flashcalc.html

 

[Crush Coral]

Thanks,

Now that my mag is up to where it should be I will monitor it to see how fast my tank depletes it.

 

[zoolan70]

I like to add mag to my water change water...it doesn't take much, and that seems to always keep me around that 1300 target. It is also easier to make it part of the water mixing routine...for me at least.