Calcium levels

Adam113 · May 7, 2017

I have a 29g cube, and added a small chalice and I also have some LPS, so I figured it was time to check my calcium and dose as needed. This was about two months ago. My calcium started at around 350 or so. Over the next few days I gradually brought it up to around 420. That's the last time I dosed. Over a month and a half ago. I check it every water change, and up until even today, it's right around the 400+ mark.

Can a tank that wasn't naturally keeping the calcium up at 400+ levels begin to maintain after being "jump started" by a calcium dose?

Randy Holmes-Farley · May 7, 2017

Are you monitoring and dosing alkalinity? Calcium will not decline if alkalinity is not declining or being dosed.

Maybe you just have little calcification. It may have been "low" initially just due to the salt mix at the salinity you are using.

Adam113 · May 7, 2017

Randy Holmes-Farley said:
Are you monitoring and dosing alkalinity? Calcium will not decline if alkalinity is not declining or being dosed.

Maybe you just have little calcification. It may have been "low" initially just due to the salt mix at the salinity you are using.

I don't monitor alkalinity as often. I don't exactly understand the correlation yet to be honest. I figured if calcium wasn't fluctuating, either was alkalinity. My KH around 7.5 when I started dosing calcium.

Randy Holmes-Farley · May 7, 2017

Adam113 said:
I don't monitor alkalinity as often. I don't exactly understand the correlation yet to be honest. I figured if calcium wasn't fluctuating, either was alkalinity. My KH around 7.5 when I started dosing calcium.

It's both, but alkalinity is way more sensitive to over or under dosing because there is a relatively huge reservoir of calcium in seawater that holds it much more steady than alkalinity.

If you start at 9 dKH and 450 ppm calcium, a balanced decline is to about 6.2 dKH and 432 ppm calcium. That alk change is easily detected, but the calcium change is likely lost in the noise of many calcium kit results.

Adam113 · May 7, 2017

Randy Holmes-Farley said:
It's both, but alkalinity is way more sensitive to over or under dosing because there is a relatively huge reservoir of calcium in seawater that holds it much more steady than alkalinity.

If you start at 9 dKH and 450 ppm calcium, a balanced decline is to about 6.2 dKH and 432 ppm calcium. That alk change is easily detected, but the calcium change is likely lost in the noise of many calcium kit results.

So KH is calcium hardness, correct? Is this also dKH? Is that alkalinity?? This is one of those things in reefing I haven't quite grasped.

Randy Holmes-Farley · May 7, 2017

For our purposes, total alkalinity and carbonate alkalinity and dKH are all the same thing. In reality there are technical differences that don't matter to you right now. It is a crude measure of the bicarbonate and carbonate available to corals to calcify and also buffer against pH changes. It can be in units of dKH or meq/L or ppm calcium carbonate equivalents (but there is no calcium involved so that's a stupid unit). 1 meq/L = 2.8 dKH = 50 ppm calcium carbonate equivalents.

Calcium hardness isn't a term we use much in reefing, but it is a measure of the calcium ions in solution. Its more of a freshwater term. We more frequently just call it the calcium concentration because we often measure in different units (ppm or mg/L of calcium ion).