Increasing Mag

[Eric the half-bee]

Randy, I am trying to up my mag in my 400 gal. Current params are pH8.1, Ca2+ 400, phospates and nitrates near undetectable. I run a Ca2+ reactor. Via a Natureef Mag test kit, the hardness is 6.31 % CaCO3 and mag is 1284. Via a Aquar. Pharm. test kit, the KH reads 17-18. If I increase the mag, will that benefit the Ca2+ level, since I cannot raise it beyond 400. 2ndly, I added 475 cc of Seachem mag supplement one time and saw no change. How much do I need to add to bump the mag?

 

[Randy Holmes-Farley]

If the magnesium is presently 1284 ppm, I don't see a reason to raise it. That almost exactly matches seawater. But if you want to raise it, you'll need a substantial amount of either a DIY or a commercial magnesium supplement. This calculator shows that it takes a very large amount to boost magnesium:

Reef chemicals calculator
http://home.comcast.net/~jdieck1/chem_calc3.html

6.31 % CaCO3

I don't know what that means.

The alkalinity is quite high, and one cannot use a CaCO3/CO2 reactor to boost calcium for this very reason; each 18-20 ppm rise in calcium would be accompanied by a 2.8 dKH rise in alkalinity. You need to use calcium chloride if you want to boost calcium.

This has more:


Solving Calcium and Alkalinity Problems
http://www.advancedaquarist.com/issues/nov2002/chem.htm

 

[Eric the half-bee]

I'm not familiar with the percentage reading either. That is directly from the Natureef tble included. Will increasing the mag benefit me in any way? Should I back off the Ca2+ reactor output to bring the KH down? Does a high alk concern you? Also, so you're saying I have to use kalk or use CaCl to bring up the Ca2+.

 

[Randy Holmes-Farley]

I see no reason to boost the magnesium. I'd back off a bit on the reactor to allow the alkalinity to drop, and boost calcium with calcium chloride , if you want it higher.

 

[Eric the half-bee]

OK, if I leave the Ca2+ reactor at the current setting, will the high alk cause problems over time? Besides burning through reactor media and CO2 faster? BTW, the pH I run the reactor is 6.9 - 7.1 per my LFS rec. Is that too low a pH? 2ndly, I'm guessing a kalk reactor is not the desirable way to boost the Ca2+ due to inc. the alk also? Last, what commercial product do you use for CaCl?

 

[Randy Holmes-Farley]

yes, that high of alkalinity may cause problems. Some folks certainly think it does. I am not certain, but I see no reason to leave it there.

Forget the ph and just drop the CO2 addition rate by half and see what that does over a few days. ph in the reactor is not the goal, the tank alkalinity is.

For a one time boost to calcium, Dowflake is fine, as are products from many hobby companies such as ESV and Kent.

 

[robrich342]

Randy would you back off on the effullent drip count or cut down on the co2 bubble count ?

 

[Eric the half-bee]

OK. I'm guessing the frequency of addition of any CaCl product to maintain a 450ish level is going to vary from tank to tank, correct?

 

[bertoni]

Yep!

 

[Randy Holmes-Farley]

Randy would you back off on the effullent drip count or cut down on the co2 bubble count ?

CO2 bubble count.

 

[robrich342]

Thanks Randy, I have a smaller but similar issue.

 

[Randy Holmes-Farley]

You're welcome.

Let us know how it works out.