Very low Calcium levels
 

Hey everyone,

So I started running a doser last weekend and my calcium is really low. My alk is at 10 (where it always has been) and my magnesium is at 1250, but my calcium is at 240. Any ideas on how to correct this?

Im currently mixing up a 30 gallon water change that I will do tomorrow. Not really sure is there is anything else that can be done, any suggestions?

A couple quick questions come to mind:
What salt are you using?
What are you dosing thus far, how much and when?
What's your tank size (total water volume) and composition (sps, LPS, clams etc)?

What test are you using? Have you compared it to a known sample?

Ive been using instant ocean for the last year and a bit, and I do water changes every week (25 gallons)

Im dosing seachem reef advantage (approximately 12 teaspoons in 1L) and brightwell alkalin8.3 (14 tsp in 1L) spread out over 1 week. Also I use a low concentration of kalkwasser in my ATO to even out any alk swings.

It is a SPS based tank, and I have only manually dosed in the past. 80% of my corals are still frags.

I use ELOS and API test kits, both read out exactly the same. I compared this to my freshly mixed saltwater which is testing at the correct levels.

Don't kill those frags!! :)

Lol I think they will be okay for the night!

Are you adding the Kalk slowly? Adding it too fast can actually pull your Ca down rather than push it up. Also 240ppm Ca seems impossibly low, I would double check that result.
Dan

absolutely:)

Double checked 3 times with elos, and twice with API test kits.

It is a very low dose of kalk. My ATO only adds 5 gallons of water a week and only has 2 tablespoons in the 5 gallons of water. It has never given me any issues before (started doing it 4 months ago), my levels have been pretty stable up until now.

you have corals?

Yup, probably 60+ frags and 8 colonies of SPS and 5 colonies of LPS in the tank. Plus a bunch of oddball corals.

Are you getting any precipitation of any kind on your pumps? I had a problem on my last tank that involved me constantly testing really low levels of calcium, which in turn led me to up the rate I was dosing. THe problem was actually that I was dosing in the wrong ratios, putting in too much alk. It was driving a precipitation reaction. I only figured out what was going on when my pumps all failed in the same week.

Can't see any kind of precipitation but ill pull some pumps out and double check.

I would say (with a fair bit of confidence) corals are not able to pull Ca down to 240ppm (please correct me if you think otherwise) ... I let mine slide down to 300 a while back and was losing frags by the handful but I may have had additional stresses involved. Also, I don't think Ca is going to ppt out at levels anywhere near that low, unless perhaps there is something else going on (like large pH swings from the Kalk).

I am going to throw an idea out for comment to the group: what about an electrical ground? I don't remember my chemistry well enough (repressed memory I suspect) to say if a charge on your tank would promote Ca precipitation. A cheap (maybe $20) grounding probe should be available from your LFS and might be a good idea regardless. For the amount of Ca your tank appears to be consuming you should see it on everything! You can also check your pH upon addition of your Kalk (or anything else for that matter) to see if the swings are substantial (maybe you manually replicate a typical dose if you don't want to wait around for the ATO).

Dan