Calcium and Mg rising with Ca reactor, steady Alk

foxt · Nov 1, 2018

I am running reborn + remag in a Ca rx at pH 6.5. I am able to maintain alk at a steady 8 dkH with about 90ml/min effluent at the moment, but Ca gradually increases over time and Mg also seems to increase but perhaps at a slower rate. I use Tropic Marin Pro Reef, and the baseline for that when I mix it is usually about Ca 450 and Mg 1350 at 35ppt. I don't do frequent water changes (as in I only do them when I need to bring Ca down). The pH of the tank ranges between 7.7 - 8.1.

Ca is at now about 640, Mg 1440. Latest ICP test also shows elevated Sr at 18mg/l. I do not see any precipitate on pumps, etc. When I get to this point, I will do some water changes with Tropic Marin Pro Reef to lower Ca back down under 500 without affecting Alk. But why do Ca and Mg ramp up over time, and at different rates, if I am holding alk steady?

I have read Randy's stuff on the relationship of these elements. First, I thought that perhaps Ca was rising with steady alk because I was seeing the effects of Mg and Sr replacing Ca in the calcium carbonate structure. But Mg and Sr are also elevated. Then I thought perhaps I was seeing the effects of decreasing alk because of nitrate export - but I am not doing water changes or using other methods to export nitrate.

So, what gives?

Cory · Nov 1, 2018

foxt said:
I am running reborn + remag in a Ca rx at pH 6.5. I am able to maintain alk at a steady 8 dkH with about 90ml/min effluent at the moment, but Ca gradually increases over time and Mg also seems to increase but perhaps at a slower rate. I use Tropic Marin Pro Reef, and the baseline for that when I mix it is usually about Ca 450 and Mg 1350 at 35ppt. I don't do frequent water changes (as in I only do them when I need to bring Ca down). The pH of the tank ranges between 7.7 - 8.1.

Ca is at now about 640, Mg 1440. Latest ICP test also shows elevated Sr at 18mg/l. I do not see any precipitate on pumps, etc. When I get to this point, I will do some water changes with Tropic Marin Pro Reef to lower Ca back down under 500 without affecting Alk. But why do Ca and Mg ramp up over time, and at different rates, if I am holding alk steady?

I have read Randy's stuff on the relationship of these elements. First, I thought that perhaps Ca was rising with steady alk because I was seeing the effects of Mg and Sr replacing Ca in the calcium carbonate structure. But Mg and Sr are also elevated. Then I thought perhaps I was seeing the effects of decreasing alk because of nitrate export - but I am not doing water changes or using other methods to export nitrate.

So, what gives?

It sounds like the media your dissolving isnt balanced. What exactly is reborn made of? If its skewing calcium compared to alkalinity then it isnt made of the right stuff.

Cory · Nov 1, 2018

How much remag to rebron did you put in it? Remag looks like dolomite.

foxt · Nov 1, 2018

Reborn is aragonite - old skeletons. I used about 1:9 ratio of Remag to Reborn.

Cory · Nov 1, 2018

foxt said:
Reborn is aragonite - old skeletons. I used about 1:9 ratio of Remag to Reborn.

Id suspect that you put too much dolomite in conisdering calcium is rising. The old skeletons should be balanced and not be a concern.

Heres what Google says about dolomite if thats what remag is made of:

"Calcium magnesium carbonate. The amount of calcium and magnesium in most specimens is equal, but occasionally one element may have a slightly greater presence than the other. Small amounts of iron and manganese are sometimes also present"

So sometimes one can be higher. The question is how much higher?

foxt · Nov 1, 2018

Both the Ca and the Mg are rising, along with Sr, and alk is steady. Wouldn't that suggest that something is consuming alk at a faster rate than Ca, Mg, and Sr? Randy references a process tied to nitrate that would have this effect, but my system doesn't match the other characteristics that he describes for that process.

I followed what others have done with the combination of Reborn + Remag, and have to believe that this recipe isn't to blame because it seems to work for other folks. What else would produce these conditions?

Randy Holmes-Farley · Nov 3, 2018

There's no reason the calcium AND magnesium could rise unless you have other sinks for alkalinity than calcium carbonate. Such as a sulfur denitrator or rising nitrate.

Magnesium will rise with too much dolomite in the reactor (remag, for example).

I'd double check the calcium kit somehow.

foxt · Nov 3, 2018

Thanks Randy.

Nitrates are not rising. The differences in my Mg readings are 6%, which could be small enough to ignore? It's the rise in Ca (450 to +600) that are causing my concern. ICP tests confirm the readings, as do different lots of Ca test kits. I get various different readings from test to test, but they all trend higher by at least 30% over this time span (about 3 months).

If I conclude that Mg isn't really moving, but Ca is rising, does that bring any likely causes into focus?

Randy Holmes-Farley · Nov 4, 2018

foxt said:
Thanks Randy.

Nitrates are not rising. The differences in my Mg readings are 6%, which could be small enough to ignore? It's the rise in Ca (450 to +600) that are causing my concern. ICP tests confirm the readings, as do different lots of Ca test kits. I get various different readings from test to test, but they all trend higher by at least 30% over this time span (about 3 months).

If I conclude that Mg isn't really moving, but Ca is rising, does that bring any likely causes into focus?

Really only five possibilities that I can think of, besides testing error:

1. That there is some other sink for alkalinity in your system, rather than just precipitation and consumption of calcium carbonate.
2. The magnesium really isn't stable and is declining due to inadequate remag (see my situation below). Calcium will rise a little faster than magnesium drops (with alk steady). Magnesium may also be held up by water changes.
3. Your salt mix or other additives are adding the calcium, not the reactor
4. Your top off water may contain calcium (tap water can, for example).
5. Salinity is creeping up.

I had a similar situation, where I used pure calcium hydroxide for all calcium and alk. In such a scenario, the calcium slowly rises because some magnesium gets into the calcium carbonate in place of some of the calcium. I used a lower calcium mix (normal IO) and it worked out perfectly.

foxt · Nov 4, 2018

Thanks Randy.

1. is there a reference you can point me to for other possible sinks of alk?
2. to evaluate this, should I try dosing Mg a little while to see if Ca stops rising so fast?
3. I don't do water changes on a regular basis, so I don't think it can be the salt. Only other additives, besides the reborn and remag, are red sea energy a + b, and food
4. this could be an interesting idea. I use RODI water, and it is sourced from my well. I don't have an abnormally high Ca content in my well - TDS in is usually below 100, and TDS out is always 0. But still, I recall reading something somewhere - perhaps from you - that even with TDS 0, there could be Ca in the water?
5. I don't see a change in salinity, and have an ATO that replaces for evap.

foxt · Nov 6, 2018

I am thinking of turning off the Ca reactor and dosing alk through ESV B-ionic part 1 only. This should let me maintain alk while letting Ca fall on it's own. Correct?

Martin Kuhn · Nov 6, 2018

Assuming that your Ca, Alk and Mg measurement is ok,
Dosing Alk only for a certain time is exactly what I recommend.

It can be B-Ionic, but also any other Alk raising 2/3 part or even only soda or soda ash

foxt · Nov 6, 2018

Thanks. I have the B-Ionic on hand, so I'll start with that and closely monitor Ca, Alk, and Mg. Hopefully Ca and Mg will come down together over the next few weeks as I hold Alk steady.

If/when I get back to Alk 8, Ca 450 and Mg 1350, I'll have to decide how to proceed. That's where I was when I started the reactor up, but Ca and Mg crept up over several months. If I use the reactor again, I need to do something different to leep everything in balance.

Martin Kuhn · Nov 6, 2018

That’s one of the downsides of a Ca reactor you simple have to accept (... or not).
Each tank is different.
Some tanks consumption is different from Ca / Alk being balanced. Here the preferred option is to adjust the reactor to the one with the lower consumption AND dose the other one additionally.

If Mg is raising to much, the recommendation is to lower the concentration of the Mg containing granulate in your reactor. Maybe even down to 0.

Cory · Nov 7, 2018

If nothing else has cha ged besides the addition of this calcium reactor media, id suspect it.

foxt · Nov 8, 2018

I am using a mix of Reborn and Remag, primarily because there are posts on R2R about good results from that mix. I have taken the reactor offline and am dosing just alk now, waiting to see how Ca and Mg react. It's too soon to tell, only been a few days and my alk consumption is about 1 dKH per day so the Ca and Mg are going to take a while to come down.

foxt · Nov 12, 2018

After 6 days of dosing only alk, Salifert Ca test showed a drop of about 40 ppm, or 6-7 ppm per day. Since a 1dKH alk drop should correspond to a 6.4-7.1 ppm Ca drop in a balanced system, I should have about a 1 sKH drop in alk every day. I seem to be consuming slightly more alk than that, about 1.5-1.8 dKH per day.

Granted all of these numbers could still work out to be in balance after I take into consideration the margin of error in each test. But all things being equal, this short period of dosing only alk to see what my Ca consumption rate is does seem to confirm that my alk consumption is higher than it would be if it were balanced with Ca. That's also what the levels indicated when I was running the Ca reactor.

So, as Martin suggested, I may need to run the Ca reactor to meet the Ca demand, and dose alk on top of that. I am going to let this play out over a full month to see if the ratio I have observed so far holds true over a longer period of time. I also need to observe the change in Mg levels, since I haven't been testing that during this period.

How unusual is it that alk and Ca and Mg consumption are not balanced?

Martin Kuhn · Nov 12, 2018

From my experience that is not unusual at all.
I know of many tanks that behave like this.

My own tank nearly had the same consumption like yours. This was the reason why after some time puzzeling around with a Shuran Jetstream, I switched over to dosing. This solved the issue for me. All in all the effort for the Al Ca Mg from this time reduced for me as the levels became stable and I got rid of correcting what was not ok using the reactor.

foxt · Nov 14, 2018

Thanks for the reply.

Tested Mg today, and it is falling at a slower rate than Ca, which is what I expected. It is quite elevated, at about 1500 ppm, but that's not a cause for concern. I am just going to keep dosing only alk and wait and see how long it takes for Ca to come down to 450. At the rate I am going, that should take another week or so.