Unbalanced Dosing

[Randyp79]

I can't figure out why my alkalinity is being used up so much faster than my calcium. Here are the details...

180 gallon total volume
Alk 7.7
Calcium 500
Mag 1450
pH 8.3
Salinity 35 ppt
PO4 0
NO3 1-2 ppm

So, I've been getting by with kalkwasser in my ATO for several months, which kept my calcium and alkalinity stable at 500 and 10 dkh. I tested for mag and noticed it had dropped to about 1200. Over the next few weeks I raised my mag levels using MgCl2. This caused my alkalinity to drop to 7.7, which is where I want it anyway, but my calcium stayed at 500. I soon noticed that my alkalinity was still dropping, so I started dosing Randy's alkalinity recipe 1. I am now up to 40ml per day of alk dosing to keep alk stable at 7.7 dkh. I don't dose any calcium, which has stayed at 500 the entire time. I have confirmed these levels with multiple test kits, Red Sea and Salifert. Any ideas or reasons for the unbalanced Dosing?

TIA
Randy

 

[Gator1970]

following along - I have the same issue with my two part dosing - I have only been dosing alk over the past 1.5 weeks because calcium is not being used up at the same rate.

 

[DipSpit]

I literally just went through this.

Are you doing water changes? That could be replenishing that calcium, but not the alkalinity?

Did you start using GFO? other media? I used BRS High Capacity GFO and upon start I had an Alkalinity drop of 1.3 dKh daily as opposed to the normal .6 dKh I normally see.

For me - i removed GFO and it just stabilized itself over the period of a week.

 

[DipSpit]

following along - I have the same issue with my two part dosing - I have only been dosing alk over the past 1.5 weeks because calcium is not being used up at the same rate.

Chemically that isn't possible I don't think. Corals need the Alkalinity to be able to utilize the Calcium and can only use one with the presence of the other - unless I am vastly mistaken. There must be other variables here.

Eliminate them all (other dosing, water changes within reason, Carbon, GFO, anything you THINK may be a factor) and start from the ground up would be my best advice, and what I did. Add each variable back and measure post-addition to see impact. Evaluate accordingly.

 

[Randyp79]

I do a 20 gallon water change every 2 weeks. I do run gfo and have for over 1 year. I really don't want to take the gfo offline for fear of algae bloom, I'm a heavy feeder.

 

[Randyp79]

BTW, all my sps are super happy with fast growth and great polyp extension. I have some new frags that have encrusted their plugs in just 2-3 weeks. I test alk everyday just to make sure I'm on top of things and it doesn't swing.

 

[Gator1970]

Chemically that isn't possible I don't think. Corals need the Alkalinity to be able to utilize the Calcium and can only use one with the presence of the other - unless I am vastly mistaken. There must be other variables here.

Eliminate them all (other dosing, water changes within reason, Carbon, GFO, anything you THINK may be a factor) and start from the ground up would be my best advice, and what I did. Add each variable back and measure post-addition to see impact. Evaluate accordingly.

Water changes average about 10 per cent per week, maybe a tad less. I did start GFO about 2 weeks ago - could that be the source of the decreasing alk with no decreasing calc? I'm wondering if its possible that the calc portion of my two part is a extra strong batch so maybe it isn't balanced with the alk component? I know the alk component must be fairly accurate because alk changes based on dosages calculated using Randy's calculator have been pretty much spot on.

 

[DipSpit]

BTW, all my sps are super happy with fast growth and great polyp extension. I have some new frags that have encrusted their plugs in just 2-3 weeks. I test alk everyday just to make sure I'm on top of things and it doesn't swing.

There has to be something that changed. Have to tested the WC water?

 

[DipSpit]

Water changes average about 10 per cent per week, maybe a tad less. I did start GFO about 2 weeks ago - could that be the source of the decreasing alk with no decreasing calc? I'm wondering if its possible that the calc portion of my two part is a extra strong batch so maybe it isn't balanced with the alk component? I know the alk component must be fairly accurate because alk changes based on dosages calculated using Randy's calculator have been pretty much spot on.

GFO could very well be the source of the alk drop. I use an AWC also and non buffered top off.

Essentially what was happening was the AWC system was keeping that Calc stable but the GFO was sucking down the Alk.

 

[eliramos]

Sounds like a bunch of mad scientists on here.
Following as I have had similar problems in the past!

 

[DipSpit]

Sounds like a bunch of mad scientists on here.
Following as I have had similar problems in the past!

Trying to fit thousands of years of unique aquatic evolution into a glass box and make it flourish? We're all mad scientists.

 

[Nano sapiens]

From a Randy Homes-Farley article on this subject:

http://reefkeeping.com/issues/2004-12/rhf/index.php

If an aquarist is supplying a balanced additive to his aquarium, and calcium seems stable but alkalinity is declining, it may very well be that what is needed is more of the balanced additive, not just alkalinity.

Excerpt:

Apparent Excess Demand for Alkalinity

One of the most common complaints of new aquarists is that their aquaria seem to need more alkalinity than their balanced additive system, such as limewater, is supplying. While there are reasons this may actually be the case over the long term (these will be detailed later in this article), frequently these aquarists are seeing a "chemical mirage" rather than a real excess demand for alkalinity.

One of the interesting features of seawater is that it contains a lot more calcium than alkalinity. By this I mean that if all of the calcium in seawater (420 ppm; 10.5 meq/L) were to be precipitated as calcium carbonate, it would consume 21 meq/L of alkalinity (nearly 10 times as much as is present in natural seawater). In a less drastic scenario, let's say that calcium carbonate is formed from aquarium water starting with an alkalinity of 3 meq/L that it is allowed to drop to 2 meq/L (a 33% drop). How much has the calcium declined? It is a surprise to many people to learn that the calcium would drop by only 20 ppm (5%). Consequently, many aquarists observe that their calcium levels are relatively stable (within their ability to reproducibly test it), but alkalinity can vary up and down substantially. This is exactly what would be expected, given that the aquarium already has such a large reservoir of calcium.

I had the same issue a number of years ago. Sure enough, adding a bit more Kalkwasser, to the point where alkalinity remained stable, did the trick. Calcium should remain stable for the short term, but will likely rise slightly over the long term (weeks to months).

 

[Gator1970]

From a Randy Homes-Farley article on this subject:

http://reefkeeping.com/issues/2004-12/rhf/index.php

If an aquarist is supplying a balanced additive to his aquarium, and calcium seems stable but alkalinity is declining, it may very well be that what is needed is more of the balanced additive, not just alkalinity.

Excerpt:

Apparent Excess Demand for Alkalinity

One of the most common complaints of new aquarists is that their aquaria seem to need more alkalinity than their balanced additive system, such as limewater, is supplying. While there are reasons this may actually be the case over the long term (these will be detailed later in this article), frequently these aquarists are seeing a "chemical mirage" rather than a real excess demand for alkalinity.

One of the interesting features of seawater is that it contains a lot more calcium than alkalinity. By this I mean that if all of the calcium in seawater (420 ppm; 10.5 meq/L) were to be precipitated as calcium carbonate, it would consume 21 meq/L of alkalinity (nearly 10 times as much as is present in natural seawater). In a less drastic scenario, let's say that calcium carbonate is formed from aquarium water starting with an alkalinity of 3 meq/L that it is allowed to drop to 2 meq/L (a 33% drop). How much has the calcium declined? It is a surprise to many people to learn that the calcium would drop by only 20 ppm (5%). Consequently, many aquarists observe that their calcium levels are relatively stable (within their ability to reproducibly test it), but alkalinity can vary up and down substantially. This is exactly what would be expected, given that the aquarium already has such a large reservoir of calcium.

I had the same issue a number of years ago. Sure enough, adding a bit more Kalkwasser, to the point where alkalinity remained stable, did the trick. Calcium should remain stable for the short term, but will likely rise slightly over the long term (weeks to months).

This makes sense, but if I am adding what should be a balanced 2 part additive then call and alk should deplete at the same rate and need to be replenished at the same rate, no? That is supposed to be one of the benefits of a two part system, I always thought. I'll continue to dose alk only and monitor calc - hopefully it stabilizes eventually to the point where depletion of each is in sync.....

 

[Randyp79]

This makes sense, but if I am adding what should be a balanced 2 part additive then call and alk should deplete at the same rate and need to be replenished at the same rate, no? That is supposed to be one of the benefits of a two part system, I always thought. I'll continue to dose alk only and monitor calc - hopefully it stabilizes eventually to the point where depletion of each is in sync.....

This is exactly what I was thinking...

My kalkwasser in my ATO is saturated and no more will dissolve.

I'm just going to continue to do the same, dosing only alk until things stabilize.

 

[DipSpit]

This makes sense, but if I am adding what should be a balanced 2 part additive then call and alk should deplete at the same rate and need to be replenished at the same rate, no? That is supposed to be one of the benefits of a two part system, I always thought. I'll continue to dose alk only and monitor calc - hopefully it stabilizes eventually to the point where depletion of each is in sync.....

Bingo - it "should" even out. But I really would eliminate all variables to begin.

 

[Nano sapiens]

This is exactly what I was thinking...

My kalkwasser in my ATO is saturated and no more will dissolve.

I'm just going to continue to do the same, dosing only alk until things stabilize.

If your demand for Ca and Alk is at it's limit using Kalkwasser, then adding vinegar will allow more of the product to dissolve (up to a point, 10% or so if I remember correctly). A 2-part can be used in addition to the Kalkwasser, too, if Kalkwasser alone isn't enough.

 

[Randy Holmes-Farley]

GFO could very well be the source of the alk drop. I use an AWC also and non buffered top off.

Essentially what was happening was the AWC system was keeping that Calc stable but the GFO was sucking down the Alk.

I think it only reduces alk in a balanced fashion with calcium due to increased precipitation of calcium carbonate. It's just that alk appears to drop more because of how much calcium is already in seawater.

 

[Randyp79]

I think it only reduces alk in a balanced fashion with calcium due to increased precipitation of calcium carbonate. It's just that alk appears to drop more because of how much calcium is already in seawater.

Randy, what do you suggest as a course of action?

 

[Hans-Werner]

The only reason I can think of why alkalinity could be consumed in an unbalanced and unstoichiometric ratio is nitrification. All other reason why it may seem so are already given by Randy and DipSpit.

 

[Randy Holmes-Farley]

Randy, what do you suggest as a course of action?

I'd dose both parts of the two part roughly equally to maintain alkalinity unless calcium rises up to about 550 ppm, at which point I'd dose just the alk part and let the calcium decline on its own.