Calcium is Low

[Scottiemac]

180g tank w/ 30g sump. Mixed reef.

I run a kalk reactor and a calcium reactor with 2 little fishes media (can't remember which style). I also have a refugium reactor and an algae scrubber; not sure if those matters for this question but am putting it out there just the same. There's a 1 gallon a day continuous water change going on with Reef Crystals mixed to a high salinity of 38psu. That AWC has only been going on for a few days.

I'm finding that my calcium is low and it won't rise. It had been under 250ppm on the Trident. I've managed to get it as high as 355 once, but typically it stays in the 330-340 range. This is with a daily 60ml dose of FM Balling Calcium.

Meanwhile, my Alkalinity is hovering around 10.24. Usually I turn the reactor off at 10, but in trying to get the calcium up I removed that line. Magnesium is also low at 1130, but this isn't the end of the world. I'm more concerned with calcium.

I do have a batch of AFR powder to mix up, but that'll raise my Alk and so I'm reluctant to do so.

Any suggestions?

 

[Randy Holmes-Farley]

Unless you are adding alkalinity in some other fashion than the kalk and the calcium reactor, I expect the calcium testing is not accurate. There's no mechanism for calcium to deplete along without alk depletion, and the kalk is adding a bit more calcium than alk.

I'd stop adding calcium and confirm the trident reading.

 

[Scottiemac]

Unless you are adding alkalinity in some other fashion than the kalk and the calcium reactor, I expect the calcium testing is not accurate. There's no mechanism for calcium to deplete along without alk depletion, and the kalk is adding a bit more calcium than alk.

I'd stop adding calcium and confirm the trident reading.

I don't have another means of testing as the Hanna test isn't reliable. What I did do, though, was to add 480ml of the FM calcium. It raised my CA from 335 to 470 (I accidentally left the pump on for 1m longer than intended).

This is pretty close to the increase I would have expected, which implies that if the test wasn't accurate, at least it's consistent.

 

[Randy Holmes-Farley]

I don't have another means of testing as the Hanna test isn't reliable. What I did do, though, was to add 480ml of the FM calcium. It raised my CA from 335 to 470 (I accidentally left the pump on for 1m longer than intended).

This is pretty close to the increase I would have expected, which implies that if the test wasn't accurate, at least it's consistent.

That is not convincing to me. You can get a test at the LFS, or get a Salifert kit, or send out for an ICP.
:)

You can also test the trident on some new salt water or a standard.

 

[BryanM]

I tend to agree with Randy, seems pretty unlikely calc was that low with the other info given.

I would get a salifert test kit to try and verify.