Equal Parts Alk and CA in 2 Part Dosing

[jdinovo]

I've heard from many sources that when doing 2 part dosing one should have equal amounts of Alk and CA in most circumstances.

My question is what does that mean? Since solutions can be made up at different concentrations what does it mean to be equal? I'm sure there is some chemical answer that I don't know, and I would appreciate any enlightenment! Thanks.

 

[mahindra.dev]

BRS Video on 2part Hope that video helps.

 

[beaslbob]

another link:

http://reefkeeping.com/issues/2006-02/rhf/index.php

in that system you first do a one time correction to get things where they should be.

you then mixup 1 gallon dosing bottles. one for calcium, one for alk one, for magnesium.

Then you measure alk and when it drops you dose equal amount of the calcium and alk solutions. After using a gallon of calcium and alk you dose magnesium.

This uses calcium choride, baking soda, and Epsom salts and magnesium chloride. Epsom salts and baking soda from grocery stores/drug stores. Calcium chloride is ice melter and also available from redimix companies. Magnesium chloride is also an ice melter but harder to obtain. I get mine from a local industrial supply firm. calcium chloride and magnesium chloride are about $15-$20 for a 50 pound bag.

my .02

 

[jdinovo]

another link:

http://reefkeeping.com/issues/2006-02/rhf/index.php

in that system you first do a one time correction to get things where they should be.

you then mixup 1 gallon dosing bottles. one for calcium, one for alk one, for magnesium.

Then you measure alk and when it drops you dose equal amount of the calcium and alk solutions. After using a gallon of calcium and alk you dose magnesium.

This uses calcium choride, baking soda, and Epsom salts and magnesium chloride. Epsom salts and baking soda from grocery stores/drug stores. Calcium chloride is ice melter and also available from redimix companies. Magnesium chloride is also an ice melter but harder to obtain. I get mine from a local industrial supply firm. calcium chloride and magnesium chloride are about $15-$20 for a 50 pound bag.

my .02

Thanks. I guess my question comes from the "mixing" part. What role does concentration play, and how is it accommodated? I can make up a salt mix at 20ppm, 30ppm, or 35ppm. A liter of each of these does not contain the same amount of salt. I'm taking it on faith that when BRS sends out their 1 gallon mixing packets they have taken this into account so that equal liquid amounts are the same as equal amount of ALK and CA, but I would still like to understand it better.

 

[beaslbob]

If you go to the link complete mixing instructions for the one gallon dosing liquids are given. It does assume 1.025 sg tho.
What should happen is the drop in alk triggering the dose should make that ok.

 

[Randy Holmes-Farley Verified Community Expert]

Some systems are made to concentrations that will not be even close to 1:1 dosing, but most are designed to be close and for those that say 1:1 dosing, such as any of my diy versions (e.g. from BRS) you should start with 1:1 dosing based on alk demand, and adjust the calcium part up or down slightly after monitoring for a while.

 

[jdinovo]

Some systems are made to concentrations that will not be even close to 1:1 dosing, but most are designed to be close and for those that say 1:1 dosing, such as any of my diy versions (e.g. from BRS) you should start with 1:1 dosing based on alk demand, and adjust the calcium part up or down slightly after monitoring for a while.

Thank you, Randy. Just saw this response now. I'm still curious as to what 1:1 really means. With the BRS solution I'm using equal volumes of solutions and I understand from your answer that that is the way that the mixes are designed. But there must be something underlying that. Equal number of atoms? of molecules? of grams of powder? I think I need to take a chemistry course!

 

[Randy Holmes-Farley Verified Community Expert]

Thank you, Randy. Just saw this response now. I'm still curious as to what 1:1 really means. With the BRS solution I'm using equal volumes of solutions and I understand from your answer that that is the way that the mixes are designed. But there must be something underlying that. Equal number of atoms? of molecules? of grams of powder? I think I need to take a chemistry course!

The reason to dose calcium and alkalinity in a reef is largely because of deposition of calcium carbonate (coral skeletons, etc.).

That deposition involves one calcum ion (Ca++) and one carbonate ion (CO3--) to form CaCO3. It is not exactly one molecule to one molecule because some magnesium and a smaller amount of strontium get into the crystal in place of some of the calcium.

Thus, a well designed two part takes these processes into account.

I give a more extensive discussion of the design of this two part here:

http://reefkeeping.com/issues/2006-02/rhf/index.php#19

 

[jdinovo]

The reason to dose calcium and alkalinity in a reef is largely because of deposition of calcium carbonate (coral skeletons, etc.).

That deposition involves one calcum ion (Ca++) and one carbonate ion (CO3--) to form CaCO3. It is not exactly one molecule to one molecule because some magnesium and a smaller amount of strontium get into the crystal in place of some of the calcium.

This, a well designed two part takes these processes into account.

I give a more extensive discussion of the design of this two part here:

http://reefkeeping.com/issues/2006-02/rhf/index.php#19

Thanks, Randy. The linked article is just what I was looking for.

 

[WWIII]

Randy, and a few others have already done all the hard work for us! They used chemistry to make the recipes balanced.

 

[Reef Jedi]

Some systems are made to concentrations that will not be even close to 1:1 dosing, but most are designed to be close and for those that say 1:1 dosing, such as any of my diy versions (e.g. from BRS) you should start with 1:1 dosing based on alk demand, and adjust the calcium part up or down slightly after monitoring for a while.

I was always under the impression (correct me if I'm wrong please) that brs 2 part should be dosed 1:1 ratio. However i have noticed CA is slightly higher then where i want it (450) while ALK is steady at (8.4). Is it okay to dose slightly less CA to bring that number closer to (420)?. If i remember an article you wrote a long time ago ALK at (8.4) would balance CA to (420) to achieve a balanced chemistry. Correct me if I'm wrong on any of this, and if it's okay to dose slightly different amounts.

 

[Randy Holmes-Farley Verified Community Expert]

I was always under the impression (correct me if I'm wrong please) that brs 2 part should be dosed 1:1 ratio. However i have noticed CA is slightly higher then where i want it (450) while ALK is steady at (8.4). Is it okay to dose slightly less CA to bring that number closer to (420)?. If i remember an article you wrote a long time ago ALK at (8.4) would balance CA to (420) to achieve a balanced chemistry. Correct me if I'm wrong on any of this, and if it's okay to dose slightly different amounts.

Yes, it is fine to dose somewhat less of either one to match the tank needs. A number of processes other than calcification add or remove alkalinity (water changes, rising or falling nitrate, top off water, sulfur denitrators, etc.) so you total demand may not exactly be 1:1. Also, many dosing pumps deliver different rates than specified, so, of course, you need off ratios to accommodate such differences.

That said, you will not ever detect any difference between reef tanks at 420 ppm calcium and 450 ppm calcium. The calcium level just doesn't seem to matter as long as it is within, say, 400-550 ppm.

 

[Reef Jedi]

Yes, it is fine to dose somewhat less of either one to match the tank needs. A number of processes other than calcification add or remove alkalinity (water changes, rising or falling nitrate, top off water, sulfur denitrators, etc.) so you total demand may not exactly be 1:1. Also, many dosing pumps deliver different rates than specified, so, of course, you need off ratios to accommodate such differences.

That said, you will not ever detect any difference between reef tanks at 420 ppm calcium and 450 ppm calcium. The calcium level just doesn't seem to matter as long as it is within, say, 400-550 ppm.

Thanks for that info! I really appreciate all your input and knowledge. I've spent countless hours reading your articles and that has helped me to have a successful reef tank.

Can I ask one more question about MG? is there really a difference between 1300-1500 mg? I've found faster growth rates with mg around 1500 as apposed to 1300. Is that because alk and ca have a better chance to bond with mg since theirs a higher concentration of it? or is this thinking and theory wrong.

 

[Randy Holmes-Farley Verified Community Expert]

Better growth of what? Most folks don't generally see that, and if alk and calcium are the same, it isn't doing anything in solution that helps them get taken up.

Som organisms, such as coralline algae that deposits a high magnesium type of calcium carbonate may grow faster in higher magnesium, but there's no real data on that, that I have seen. Just reports from reefers.

 

[Tmmste]

Thanks for that info! I really appreciate all your input and knowledge. I've spent countless hours reading your articles and that has helped me to have a successful reef tank.

Can I ask one more question about MG? is there really a difference between 1300-1500 mg? I've found faster growth rates with mg around 1500 as apposed to 1300. Is that because alk and ca have a better chance to bond with mg since theirs a higher concentration of it? or is this thinking and theory wrong.

I am interested in the role of magnesium too... I tend to stick with the "3x the amount of calcium".. my Ca is 460.. So I aim for 1480 ppm Mg. Just to prevent precipitation. However, read somewhere (cannot recall where) that a too high amount of Mg (e.g. 1500 when Ca is 420l may actually inhibit the formation of calcium carbonate by the coral.. just something I picked up, but I do not know if this is true or false.

 

[Aaronreef]

I know this is an old thread but could do with some help.
I have been using ATI essentials for a few months.
My alk I've got stable at 9.8 by dosing 3 lots of 10ml at 01:00 02:00 03:00
My calcium doesn't really change from 460 sometimes it reads higher even without dosing
I'm using Hanna checker for both tests.
Should I be dosing 30ml of calcium as well to match my 30ml of alkalinity even though my test doesn't show any drop ?
Any advice would be great

 

[Randy Holmes-Farley Verified Community Expert]

I know this is an old thread but could do with some help.
I have been using ATI essentials for a few months.
My alk I've got stable at 9.8 by dosing 3 lots of 10ml at 01:00 02:00 03:00
My calcium doesn't really change from 460 sometimes it reads higher even without dosing
I'm using Hanna checker for both tests.
Should I be dosing 30ml of calcium as well to match my 30ml of alkalinity even though my test doesn't show any drop ?
Any advice would be great

That rise without dosing is just an indication of the relative test error (unless you are experiencing salinity swings).

In general, if calcium is higher than you want, its OK to hold on dosing it. But just because it doesn't appear to fall is not a reason to avoid dosing, because the expected drop (and the offsetting rise from dosing) may also be very small.

 

[Aaronreef]

Thanks for replying.
My salinity level is stable at 35ppt.
I've been testing calcium 3 times per week for the past 4 weeks with no major changes to the results.
So I haven't dosed any as didn't want it to rise more than it is.
Do you suggest that I dose Calcium and alkalinity equally or dose perhaps half the amount calcium to alkalinity?
I could test calcium daily if it would help me

 

[Randy Holmes-Farley Verified Community Expert]

It's OK to either stop dosing calcium for a while (testing once every few days), or dose close to 1:1 and test calcium once a week or so. Adjust the calcium dosing downward if calcium rises more.