Please Help Me Understand What's Going On With Calcium and Mg

Scott07

New member
Hello,

I had started a thread in the new reefer's section a few days ago... but wanted to give an update and get some more advice... and felt this may be the more appropriate place.

I've noticed recently that my Calcium has been quite high. I haven't dosed a thing besides some buffer in my top off water for the last couple of weeks. Recent changes that have been made include adding a phosban 150 reactor w/ Phosguard... and starting a new batch of salt (same brand, reef crystals, just a new package of it). Tank is a 20 gallon long... no sump... HOB filter (AC110) containing skimmer, intake for reactor, filter floss, bag of carbon. 2nd HOB filter (AC70) converted to fuge w/ chaeto. Phosban reactor as mentioned previously.

So.. I tested calcium and magnesium again last night and am still getting strange results... Calcium is around 480 or 490. Magnesium is right about 1600. I'm not overly concerned, as I understand these are still within ranges that shouldn't hurt anything... but I'm trying to understand why this might be. I haven't dosed calcium since about 2 or 3 weeks ago... and then was keeping it around 440 or 450 and testing regularly. I haven't dosed magnesium since a couple of months ago... my salt mix has always seemed to keep it in check.

Right now I have two theories... but i'm hoping that someone w/ more experience can help point me in the right direction, and let me know if there's anything I need to do. Theory 1; Phosban reactor has removed a large amt. of phosphates from the water opening up more bonding sites or something in the water chemistry which can now absorb calcium and magnesium. Theory 2; I need to roll my bucket of salt... it may not be mixed uniformly. I dumped two of the bags you get in the 200 gal. box into the empty bucket i had from last time... thought this would be sufficient to mix it up... but maybe not? It's only my second time buying large quantities of salt...

Thanks in advance for any replies... I'd really like to at least understand why this is happening, as I'm trying very hard to promote stability in my tank... which this is not helping lol.
 
Theory 2 might be plausible. Theory one is not. :D

You may also have a batch of salt with unusually high levels, or the kit may not be giving accurate results. All of those happen, with kit errors more common than true salt issues.
 
Thanks Randy, I'll give my bucket a roll and see if that may be the cause... I'll probably test the new water I make for this weekend's WC as well, and see if I can draw any conclusions. Appreciate all the help!
 
Sounds good.

God luck and let us know what you find. :)

Hi Randy... ok, reporting back as I've now done my weekly WC. I rolled, shook, turned end over end... my bucket of reef crystals a few days ago, and made a new batch with it today. I mixed the new water to 1.025sg, as always, let it mix for a few hours, then tested magnesium and calcium. Calcium was 500, magnesium 1600.. maybe just a touch more. So I feel pretty confident now that it's the box of salt that I got.... as I'm using the exact same testing procedures as I always have.

So, I guess my question is.... will it be ok to continue to use this batch for the next 3 or 4 months and just not dose anything but alk? Or should I be concerned about my calcium and mag. being that high for a prolonged period?

As always... thank you in advance for any replies!
 
Its likely fine.

What test kit? Some find that the Red Sea kits give high readings sometimes.

I'm using red sea test kits for both calcium and magnesium. With the calcium test, I just purchased a new reagent pack and tried using those reagents to compare to the results I was getting with the current kit. If anything, I got calcium results just a touch higher. Do you know where to find an expiration date or similar on the red sea kits?

I guess before I spend more on new tests, I'll probably take a sample of my water to the LFS and see what they come up with. I'll report back....
 
You could try getting a second opinion on the Red Sea kit, but those levels are safe as is. I wouldn't worry very much, personally.
 
You could try getting a second opinion on the Red Sea kit, but those levels are safe as is. I wouldn't worry very much, personally.


Thank you bertoni. I'm not all too concerned with the levels... more so curious what's going on... and if it's error on my part or not. I suspect that it is not... as what I'm seeing happen in the tank (coraline spreading faster than previously) seems to correspond with the readings I'm getting. That said... it could of course be complete coincidince.

More or less.... i'd like to try and figure out how to keep my corals growing and happy. With these readings, I'm not dosing anything besides buffer/alk suppliment. However if they're not accurate....
 
People have reported some fairly high calcium and magnesium levels from freshly-mixed saltwater, possibly due to settling in shipment or a bad batch. If rolling your salt around doesn't change anything, I'd definitely get a second opinion on the test kits before doing much.
 
I haven't made it to the LFS to get my water checked out yet.... but did remember last night that I have an API calcium test kit laying around from before I upgraded to the Red Sea. It's about 2 years from expiration... so I'm pretty confident it should still be good. I understand the API kits are not as accurate as... well... about anything else... but thought I'd check anyway and compare results.

Calcium again tested high (480 or so) with the API kit... so I feel like this confirms my suspicions to an extent. I think i'm going to keep using the salt I have and just monitor levels closely for now. I just can't see myself throwing out that much mix unless it's causing problems in my tank. Just interesting and a little bit concerning to me that I haven't dosed calcium in weeks now and the level remains that high.

Any other suggestions/advice? I'm not sure there's really anything else i can do here, or that would be wise to do...
 
480 ppm calcium is not too high and many mixes come with substantially higher levels than that.

What salt mix are you using?

I'm using IO Reef Crystals. I agree... 480 is not particularly concerning to me, and I plan to keep using the box of salt I have. It's just curious to me that my DT water has always tested around 430 or 440 calcium which I was maintaining w/ dosing, and around 1280 or 1300 magnesium... and is now closer to 500 clacium (no dosing) and 1600 magnesium after just 3 or 4 weekly water changes.

On a side note.... I made the switch from Phosguard to GFO (phosban) this weekend and have noticed some improvement in the PE of a few of my corals which were suffering. I understand not even close to a controlled scientific study... but I am more convinced now that my corals were not reacting to lower phosphates... but rather to the Phosguard I was using.
 
I think I figured it out! Please confirm?

I think I figured it out! Please confirm?

So... I had a thought tonight after dinner; these levels would almost make sense if my salinity was out of whack.... I've been both making WC water as well as checking the salinity of my tank with a refractometer calibrated regularly with calibration fluid. So I checked it against fresh RO/DI... and what do you know... way off. After re-calibrating, I believe my DT is at 1.027

Ok, so I think I've got it... but I do have a few questions:

- this makes sense right? Calibrating w/ RO/DI I should be getting 0.00 on the scale? And my calcium and magnesium levels would make more sense at this salinity?

-how quickly should I lower salinity back down to 1.025 (target)? Is it not that big of a deal and I can do it over a day or two? Or should I stretch this out more over a week?

As always... thanks for the replies!
 
Calibrating a refractometer with RO/DI can give very inaccurate results:

http://reefkeeping.com/issues/2006-12/rhf/index.php

I would trust the calibration solution more than RO/DI, but both could be wrong.

Good read... and makes a lot of sense... although not exactly what I was hoping for. I have both a swing arm and floating hydrometer to compare to. The swing arm I place less faith in as I haven't used it since getting the refractometer. I checked my tank water this morning with both the floating hydrometer and re-calibrated refractometer. They are reading within .001 of each other so I'm hopeful that I've drawn correct conclusions.

So I'm thinking next steps are to pick up some new calibration solution, and try to calibrate my refractometer using two different data points. I'll probably do this this weekend.

Is this what you would do? Any other suggestions? Reassurance lol?

Again, thank you all... this thread has been very helpful to me so far.
 
Calibrating a refractometer with a 35 ppt calibration solution is always an appropriate action, assuming it is not a digital device that prevents it. :)
 
Calibrating a refractometer with a 35 ppt calibration solution is always an appropriate action, assuming it is not a digital device that prevents it. :)

Hi Randy,

Is calibrating w/ RO/DI necessarially that bad? I understand from the article bertoni linked why calibration solution is more accurate than RO/DI... actually pretty interesting, and I love learning something new. However, my directions do state to use "distilled water" so it's got to be at least ballpark right? Just since i've re-calibrated w/ RO/DI, everything is making more sense... my swing arm hydrometer, floating hydrometer, and refractometer are all now reading within about .001 of one another.

The circumstantial evidence (higher calcium and mag. plus RO/DI calibration off) is making me think that my calibration solution must be off.... But admittedly I don't have the experience to really know here.

Randy, are you saying you would still choose to trust the calibration solution rather than comparing against RO/DI as I've done? I've looked all over the bottle and there is no expiration date or code of any sort... so I have no idea how old it actually is, although I bought the solution less than a year ago.

And to answer your question, my refractometer is a JBJ C-Scope w/ ATC.

Look forward to your replies.... thanks!
 
Is calibrating w/ RO/DI necessarially that bad?

It is never accurate if you are measuring seawater and the device is a repurposed brine refractometer (which most were, at least until recently when some true seawater refractometers began to be sold to hobbyists). If it doesn't claim something like "true seawater refractometer", then it probably is not.

The reason is that the device measures refractive index, but the relationship between what it measures (refractive index) and what it tells you (salinity or specific gravity) is different for seawater and for brine (sodium chloride solutions). How far it is off (assuming it is a perfect brine refractometer) depends on whether it is reading in ppt (will be off 1.7 ppt, reading higher than it actually is, which is a lot) or by about a sg of 0.0003 lower than it really is (which is not that much).

That said, I can't be sure your standard is accurate either, if it has evaporated over the years or perhaps was made incorrectly.
 
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