Question for SK8R

tzylak · 10/31/2014, 01:05 PM

What do you mean about "Alk and cal will not rise if mg is low ", mentioned in you tank specs?
Please elaborate.
-I don't check my mg and alk and cal has always been low. Maybe that's the crux of my problem. . .
Thanks.

billdogg · 10/31/2014, 05:11 PM

I forget the exact reason, but yes - if your Mg is low you won't be able to dose enough of either Ca or Alk supplements to get them to come up. I had forgotten about the relationship until nudged on here. I got the Magnesium back up and the problem disappeared.

Repost your question in the Chemistry forum so Randy can give it a shot or do a quick search - I'm sure some of his past writings will come up.

Sk8r · 10/31/2014, 05:28 PM

It's like a three-legged stool, only kind of a magical one in which one leg is the standard. If you have to adjust chemistry, you can pour alk and cal in with no lasting result...unless you raise mg first. Raise that to about 1300 (which gives it some wiggle room) and THEN when you add buffer and calcium, the readings will stay where you put them until the mg runs out. I think the trick is that the alk thing is just buffer, which controls acidity/alkalinity of the seawater, which is how able it is to dissolve calcium, which is the name of the game. When you supplement calcium to the hungry stony coral, it sucks it up fast, but kalk goes on pouring calcium into the tank, and the buffer allows the water to stay at the right ph range; and the mg helps hold the buffer steady...I'm far from sure of that scenario, because I was NOT my chemistry prof's star student, but that's operationally how it works, at least.

10/31/2014, 01:05 PM	#1
tzylak Registered Member Join Date: Aug 2014 Location: Oceanside, CA Posts: 457	Question for SK8R What do you mean about "Alk and cal will not rise if mg is low ", mentioned in you tank specs? Please elaborate. -I don't check my mg and alk and cal has always been low. Maybe that's the crux of my problem. . . Thanks.

10/31/2014, 05:11 PM	#2
billdogg Registered Member Join Date: Apr 2008 Location: Grove City, Ohio Posts: 10,806	I forget the exact reason, but yes - if your Mg is low you won't be able to dose enough of either Ca or Alk supplements to get them to come up. I had forgotten about the relationship until nudged on here. I got the Magnesium back up and the problem disappeared. Repost your question in the Chemistry forum so Randy can give it a shot or do a quick search - I'm sure some of his past writings will come up. __________________ I'll try to be nice if you try to be smarter! I can't help that I grow older, but you can't make me grow up! Current Tank Info: 120 mixed reef with 40b sump, RO 150 skimmer, AI Sol Blue x 2, and a 60g Frag Tank with 100g rubbermaid sump. 2 x Kessil A360w lights, BM curve 5 skimmer

10/31/2014, 05:28 PM	#3
Sk8r RC Mod Join Date: Feb 2006 Location: Spokane WA Posts: 34,628 Blog Entries: 55	It's like a three-legged stool, only kind of a magical one in which one leg is the standard. If you have to adjust chemistry, you can pour alk and cal in with no lasting result...unless you raise mg first. Raise that to about 1300 (which gives it some wiggle room) and THEN when you add buffer and calcium, the readings will stay where you put them until the mg runs out. I think the trick is that the alk thing is just buffer, which controls acidity/alkalinity of the seawater, which is how able it is to dissolve calcium, which is the name of the game. When you supplement calcium to the hungry stony coral, it sucks it up fast, but kalk goes on pouring calcium into the tank, and the buffer allows the water to stay at the right ph range; and the mg helps hold the buffer steady...I'm far from sure of that scenario, because I was NOT my chemistry prof's star student, but that's operationally how it works, at least. __________________ Sk8r Salinity 1.024-6; alkalinity 8.3-9.3 on KH scale; calcium 420; magnesium 1300, temp 78-80, nitrate .2. Ammonia 0. No filters: lps tank. Alk and cal won't rise if mg is low. Current Tank Info: 105g AquaVim wedge, yellow tang, sailfin blenny,royal gramma, ocellaris clown pair, yellow watchman, 100 microceriths, 25 tiny hermits, a 4" conch, 1" nassarius, recovering from 2 year hiatus with daily water change of 10%.