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H20ENG
10/07/2009, 05:24 PM
A customer wants to put a second Ca reactor on a system just to dose Mg. I'm guessing dolomite media? What are the drawbacks or plusses to this?

I suggested a doser or just putting dolomite in the existing schuran ca reactor. For a roughly 700g system, what would be the best way to maintain Mg levels?

Silly question, can mg flake be used in a kalk style reactor; supersaturated then slowly fed DI water to dispense it?

Thanks all,
Chris

Logzor
10/07/2009, 07:14 PM
I never hear of people using a reactor for Mg. I would suggest a dosing pump.

Mike O'Brien
10/07/2009, 08:05 PM
With a high purity dolomite, you can usually get away with 5 to 10% mixed in the reactor. IIRC used on it's own or too much, it will drive alkalinity too high.

kybreos
10/07/2009, 09:20 PM
magnesium lowers alk...

Mike O'Brien
10/07/2009, 09:23 PM
It does ????

Not when you dissolve Dolomite it doesn't...

H20ENG
10/07/2009, 09:27 PM
Thanks, thats what I thought:)

kybreos
10/07/2009, 09:27 PM
not sure about the dolomite, but mag does lower alk

Mike O'Brien
10/07/2009, 09:30 PM
Yes and no. Some of it is, but it's role is to inhibit abiotic precipitation by poisoning the fresh crystal surface. Basically helping to keep more alkalinity in the water. That's why when Magnesium is low, it's harder to maintain adequate alkalinity and Calcium.

kybreos
10/07/2009, 09:44 PM
okay, i just read a couple articles- the reason alk doesnt go down when dissolving dolomite is because in the dolomite the alk is in relation to the mag 2 to 1.

Mike O'Brien
10/07/2009, 09:46 PM
Right and that's why I say if you use too much in the reactor, you may end up out of balance compared to just Calcium Carbonate in it.

Randy Holmes-Farley
10/08/2009, 05:53 AM
Dolomite in a reactor is a fine way to MAINTAIN magnesium, but it cannot be used to RAISE magnesium. The problem is that for every magnesium ion released from the dolomite, 2 units of alkalinity are also released:

MgCO3 ---> Mg++ + CO3--

Consequently, if one wants to raise magnesium by 100 ppm, the alkalinity will necessarily rise by 8.2 meq/L (23 dKH). The only way around this problem is to add a mineral acid (not vinegar) to the aquarium to reduce the alkalinity, and that may be more problematic than just adding magnesium in the first place.