Question on dosing

[wanwan]

Hi all i bought ca mg and kh powder from iwarna. I am using the below link from xiggie http://reef.diesyst.com/chemcalc/chemcalc.html and find that to raise 100ppm for mg i need to dose about 300g sound logical? By the way my tank size is 96 gal.

[pcw]

I'm assuming you're using MgCl2? With MgSO4 would need even more of it by weight lol. Anyway, calculating manually, 100ppm can be equated to 100 mg/dm3. 96 gallons is around 363.4 dm3. Since you're increasing the concentration by 100ppm in 96 gallons of water, the amount of Mg you would need is 363.4 x 100 = 36340mg. This is 36.34g. But this is only for Mg itself. 36.34g of Mg is around 36.34/12 = 3.028 mols. Molar mass of MgCl2 is 95.21. So by weight, the mass of MgCl2 you would need is 3.028 x 95.21 = approximately 288g (3.s.f). Quite close to 300g I suppose. But this is assuming that you're using MgCl2. Anyway I caveat this by saying that the experts should chime in first. I've never dosed Magnesium.

[wanwan]

Ok i will dose 100 g first then test water fir mg again

[pcw]

Don't dose all at once. I'm not sure what is a safe rate of increase in concentration for Mg but please dose in a slow and gradual manner in case there is some shock to your livestock.

[Angel Keeper]

It's not recommended to up Mg by more than 10 ppm in a day.

Angel Keeper