Manganese dosing

[dodgy67]

Read an article recently where Randy commented that Manganese is 28% by weight, I have just received a packet of Manganese (ll) Chloride Tetrahydrate 98% assume this is not 98% Manganese before I recalculate dosing.

Thanks in advance for any advice.

 

[bertoni]

Let's go through the math. Manganese chloride is MnCl₂. The molecular mass of the Cl part is 71.0. The Mn part is about 55. H₂O has a molecular mass of 18, and this is a tetra-hydrate, so the water part is 4 * 18 or 72. The mass per molecule is thus 198, of which 55 units are manganese, which leads to about 28% manganese by weight. To dose 1 ppm, which is about 1 mg/L, lets just say 4 mg/L of your manganese product, since 28% is close enough to 25%.

What kind of scale or measuring equipment do you have on hand?

 

[dodgy67]

This was the original thread I was following
Following this recipe by [MENTION=2791]Randy[/MENTION] Holmes-Farley

Manganese(II) chloride tetrahydrate is 28% manganese by weight.
Here's a recipe:

Dissolve 1 gram in 100o mL (grams) fresh water. Manganese = 280 ppm.
Take 1 mL (1 g) of that mix and dissolve in 1000 mL of fresh water. Mn = 0.28 ppm (=280 ug/L).
Add 1 mL of that to 100 mL of fresh water. Mn = 2.8 ug/L
Add 13.5 mL of that to 100 gallons of tank water. Conc boost to tank = 0.1 ug/L Mn.

To me the 0.1ug/L did not look right as seawater in 0.01ppm which is 10ug/L

Please correct me if i'm wrong but this is my calculation
Dissolve 1 gram in 1000 mL (grams) fresh water. Manganese = 280 ppm = 280,000ug/L

Take 1 mL (1 g) of that mix and dissolve in 1000 mL of fresh water. Mn = 0.28 ppm (=280 ug/L).
Therefore if my tank is 350L dosing 1ml would be 0.8ug/l so to get 10ug/L (0.01ppm) would require 13ml which I would dose in 1ml increments to be safe.

Doesn't appear there is a Manganese test kit around type in Manganese and you get Magnesium.

Thanks very much for your reply

 

[bertoni]

I agree that your solution is around 0.28 ppm. Dosing 1 ml per L would give you about 0.28 ppb, or 0.28 ug/L, so dosing 35 ml per L would be around 10 ppb. I think Randy's math seems correct, although the target dose is very small.

 

[dodgy67]

Jonathon thanks for confirming, but I am still confused I have been following another thread https://www.*********.com/threads/diy-manganese-calculation-help.477189/ where there is much debate on what solution to take the dose from

 

[dodgy67]

*********.com/threads/diy-manganese-calculation-help.477189/

 

[dodgy67]

it should be reef 2 reef

 

[bertoni]

I see the source of the confusion. Randy is concerned about overdosing, given the limits of detection of the measurement equipment.

If you want to dose around 10 ppb, I suggest making a 2.80 ppt solution. To make the 2.8 ppt = 2800 ppm, that's be about 10 grams of your product with enough water to make 1 L, and then 1 ml per L of tank water would add about 2.8 ppb. So it'd be about 350 ml to raise the tank to 2.8 ppb. I might try a small fraction of that, just out of general caution. Maybe someone can double-check my math.

If 10 grams won't dissolve in 1 L, we'll have to work from what does dissolve.

 

[dodgy67]

Jonathan many thanks for your help with this, as you say there is lots of confusion on various sites so i'll make up a solution and take dosing steadily. Will let you know how it goes

Many thanks again

 

[dodgy67]

Jonathan, from the original 1gm to 1 litre, I added 9 more to make up to 10 and dosed slowly over a couple of days 12ml. Several SPS did seem to stretch polyps out more, but a 50 headed Duncan closed up and my Goniapora went all droopy, left it a few more days then did a 15 Gall water change, and only today has the Duncan come out and the Goni looks better, so any dosing I do may be from the second dilution.

 

[bertoni]

Different corals often seem to respond differently to supplements. I am not sure why corals should have problems unless the manganese was actually higher than expected, or the supplement had some sort of problematic contamination. Hard to say.