Check your calcium levels in your homemade 2-part!

[vapormd]

For those using homemade two part but having trouble maintaining balanced alk and calcium, here's a possible reason:

I've been using homemade two part additive following Randy's recipes and using bulk ingredients obtained from an online vendor. Since using the homemade two part, I've found that while I was easily able to maintain stable alk levels, my calcium levels would consistently drop over the course of a week to where I'd have to supplement extra calcium. After ruling out several different possible causes (abiotic precipitation, mixing errors, etc), I decided to check out the concentrations within my homemade solutions.

To make the calcium solution, I was using two level cups of calcium chloride pellets mixed with RODI water to make one gallon total.

To make the alkalinity solution, I was using two levels cups of sodium carbonate mixed with RODI water to make one gallon total.

According to Randy's article, the calcium portion should contain 37,000 ppm calcium. In order to perform testing using our standard calcium tests (I used Salifert, API, and seachem tests as a triple check), I performed a 1:100 dilution of the part 1 solution - which should read 370 ppm.

Sample 1 (fresh mixed): 260ppm
Sample 2 (two week old solution from a different batch): 230ppm
Sample 3 (another fresh mixed): 250ppm

The solutions I was using contained about 2/3rds the amount of calcium necessary to make up a balanced additive according to Randy's recipes, which probably led to my slowly declining calcium levels over time.

I've since started using three cups of calcium chloride pellets vs two cups, and have had no further problems with declining calcium levels. Another approach would be to increase the amount of Part 1 dosed, but that would kind of take away from the point of being able to dose equal amounts every day.

BTW - I performed similar testing on the alkalinity solution, which is supposed to contain 5300 dKH, and found my solutions to be pretty much on the mark. For the dKH I had to perform a 1:1000 dilution to bring the sample into the testing range of our kits, about 5.3dKH

HTHs!

[Billybeau1]

I'll let Randy tackle this one in the AM. I'm sure he will.

[Randy Holmes-Farley]

My recipe #1 that contains 37,000 ppm calcium is made with 2 1/2 cups into a gallon of total volume (after dissolution), not 2 cups.
Here's me recipe:

"Recipe # 1, Part 1: The Calcium Part

Dissolve 500 grams (about 2 ½ cups) of calcium chloride dihydrate (such as Dowflake 77-80% calcium chloride or ESV calcium chloride; see below for substitutes and sources) in enough water to make 1 gallon of total volume. You can dissolve it in about ½ gallon of water, and then pour that into the 1 gallon container and fill it to the top with more freshwater. This solution has about 37,000 ppm calcium.
"

http://reefkeeping.com/issues/2006-02/rhf/index.php#4

FWIW, I think it unlikely that the recipe when made correctly is off significantly, but it will vary a little due to differences in bulk density of different types of calcium chloride (unless you measure by mass).


Likewise, while I do not have a specific volume recipe using sodium carbonate, 2 cups of sodium carbonate will contain substantially more alkalinity than my recipe which calls for 2 1/4 cups of sodium bicarbonate. Sodium carbonate is roughly 60% more potent on a volume basis than is sodium bicarbonate.

the recipe:

"Recipe #1, Part 2: The Alkalinity Part

Spread baking soda (594 grams or about 2 ¼ cups) on a baking tray and heat in an ordinary oven at 300°F for one hour to drive off water and carbon dioxide. Overheating is not a problem, either with higher temperatures or longer times. Dissolve the residual solid in enough water to make 1 gallon total. This dissolution may require a fair amount of mixing. Warming it speeds dissolution. This solution will contain about 1,900 meq/L of alkalinity (5,300 dKH). I prefer to use baked baking soda rather than washing soda in this recipe as baking soda from a grocery store is always food grade, while washing soda may not have the same purity requirements. Arm & Hammer brand is a fine choice. Be sure to NOT use baking powder. Baking powder is a different material that often has phosphate as a main ingredient."

Consequently, it does not surprise me that calcium does not keep up with the alkalinity that you are dosing.

[Randy Holmes-Farley]

FWIW, I would not rely much on high dilution home testing to give accurate results for these solutions.

[mille239]

I guess I will post this here as well...

If I may chime in real quick...The original poster did not mention whether he was using calcium chloride dihydrate, or calcium chloride anhydrous for the Part 1 recipe. I use the anhydrous, and according to the directions on the

www.twopartsolution.com

website, it does call for only 2 cups of the anhydrous pellets. The original poster did say he was using 'pellets' so I'm assuming he is using calcium chloride anhydrous as well.

[vapormd]

Randy,

Let me apologize! - I in no way was trying to knock your recipe, in fact your article and work with the subject has been invaluable to me. I was trying to point out that the calcium levels in certain bulk materials did not seem to me to be potentially the same as those used in your recipe.

I am not using Dowflake, but rather Dow food grade anhydrous pellets (according to the vendor). Your article suggest a 20% reduction in the amount used to make solution one with these types of products, or about 2 cups. The recipe suggested by the vendor I obtained the product from suggests the same, and so was the basis by which I had been making Part 1.

As for the home dilution methods, the method I used was serial dilution using 10 cc syringes. For the 1:100 dilution, I did two serial dilutions (1 cc sample + 9 cc diluent, mix, discard 9 cc, and then redilute), for the 1:1000, I performed three. I perform these dilutions numerous times daily in my work, and I believe done correctly, they can be accurate enough.

Also, I did find the alkalinity part 2 solution to contain an appropriate amount of alkalinity using these methods, but I guess I might have gotten lucky

[vapormd]

Blair,

Thanks, I am using anhydrous pellets.

[Randy Holmes-Farley]

OK, I think the issue is too much alkalinity in the alkalinity part, despite the test results. Did they say to use 2 cups of the sodium carbonate?

Hopefully the company actually sent you the anhydrous calcium chloride.

[vapormd]

Yup, the vendor states to use 2 cups of the sodium carbonate to make Part 2. The sodium carbonate is comprised of small pellets, rather than a powder like A&H baking powder.

Alot of people seem to obtain their materials from this vendor, so I can only hope they're selling as stated!

[Randy Holmes-Farley]

You don't have access to a scale to measure how much a cup of that material weighs, do you?

Maybe they weighed it and it is correct, but it seems like too much to me. I'll email them and ask them to pop by and comment on the amount suggested.

[Randy Holmes-Farley]

OK, I emailed them and asked them to come by, but if they only reply by email, I'll post it here.

BTW, thanks for posting the concern.

[USC-fan]

They have a sponsor forum here also.

[Randy Holmes-Farley]

They replied that they do use an especially light density sodium carbonate, so perhaps the amount is OK.
They also responded that they occasionally get folks noticing drops in one or the other over time, but not generally one way or the other. Most customers do not see such differences.

vapormd: How much of a drop in calcium are you talking about, over what period of time? What salt mix do you use and do you do water changes?

[vapormd]

My calcium would drop about 40 ppm over the course of a week, while continually dosing two part. I use a 50/50 blend of IO and Oceanic salt (which gives me a calcium of about 420), and do a 10% water change every two weeks.

Some other info (in case it's useful):
Estimated system volume of 200 gallons, barebottom, mostly mature SPS colonies. I dose 240 cc of Part 2 thru a litermeter III daily, along with 240 cc of my version of part 1 with three cups of calcium.

pH = 7.95-8.20 daily swing
Alk = 8.5 dKH
Ca = 400
Mg = 1400

[Randy Holmes-Farley]

That's a pretty big drop. Over how long a time period (how many weeks of 40 ppm per week)?

FWIW, if the 3 cup version works, I'd stick with it.

[Randy Holmes-Farley]

One additional comment about calcium testing the stock solution. I seem to recall Habib Sekha (owner of Salifert) telling me long ago that the calcium kit required some alkalinity to function (I might remember wrong ).

BUT, the Hach kit that I have that is designed to use in fresh water or salt water has a buffer addition step first thing while many marine hobby kits do not do this (I've not used them all, however). So perhaps kits designed for seawater where there is alkalinity do not work properly in calcium chloride solutions.

[vapormd]

The 40 ppm drop per week was pretty constant over the course of the past three months while I was looking for a reason.

The test kits I used seem to function correctly (meaning everything turned the appropriate colors with the addition of the reagents), and the endpoints were all pretty sharp with color changes within a drop of the endpoint, but I don't know if that truly indicates anything about whether they were functioning appropriately or not.

Maybe I could take the final dilutions and combine then, which should provide a solution of 2.65 dkH and 185 calcium, and provide some alk for the calcium test.

[Billybeau1]

Originally posted by vapormd
Maybe I could take the final dilutions and combine then, which should provide a solution of 2.65 dkH and 185 calcium, and provide some alk for the calcium test.

If you are talking about combining the 2-part, don't. They should be added to your tank separately.

What I would suggest is test your tanks calcium level, plug your numbers into the Reef Chemicals Calculator, add the required amount, then test again in an hour and see just how much your calcium raised. Then test again 24 hrs later and see where you are at.

For total water volume, try to estimate your actual water volume and not tank size. Meaning, tank + sump minus rock and sand.

Since you dose daily, what you are trying to find out is the proper amount to add to maintain calcium at your desired level.

FWIW, with a tank that large and a reasonable amount of calcium consumption, I would consider a calcium reactor. It just may solve all of your problems and require less day to day maintenance and additions.

[vapormd]

Originally posted by Randy Holmes-Farley
One additional comment about calcium testing the stock solution. I seem to recall Habib Sekha (owner of Salifert) telling me long ago that the calcium kit required some alkalinity to function (I might remember wrong ).

BUT, the Hach kit that I have that is designed to use in fresh water or salt water has a buffer addition step first thing while many marine hobby kits do not do this (I've not used them all, however). So perhaps kits designed for seawater where there is alkalinity do not work properly in calcium chloride solutions.

Originally posted by vapormd

Maybe I could take the final dilutions and combine then, which should provide a solution of 2.65 dkH and 185 calcium, and provide some alk for the calcium test.

I was addressing Randy's comment about the calcium test kits not working without some alkalinity present in the test sample. Since I was testing diluted samples of homemade part 1, which contain no alkalinity, I was trying to come up with a method for adding some alkalinity to my diluted calcium test sample to ensure the calcium test kit would work properly. It wasn't related to any actual tank dosing.

[Billybeau1]

Oh, OK. I don't think that will work but I'll let Randy answer that in the morning.

Have you considered a calcium reactor ?

[Randy Holmes-Farley]

Without my knowing exactly what's needed in any particular test kit, I'm reluctant to say too much about how to get them to work in new settings, aside from noting that people have enough problem getting them to work where they are actually intended.

While I don't think your situation is common, your solution seems simple enough and the only possible problem is slowly elevating calcium, which is not a concern if you monitor it. Diagnosing weird situations from afar has proven too complicated in the past, and this may just be one of those.

So I'd just stick with your new recipe for now.

[Fraggle Rock2]

I am curious,

I used the "often linked" calculator (http://home.comcast.net/~jdieck1/chemcalc.html)
to determine the following:

in 1 Gallon of water

to raise Ca from 1 to 37,000 ppm requires:

513.5mL of 77% Dow Flake, which is about 2 Cups. According to recipe 1 it would be 2.5 Cups or 625mL.

to raise Alk from 1 to 1900 meq/L requires:

642 mL of baking soda or 414 mL of baked baking soda. According to recipe 1 it would be 2.25 Cups or 562 mL of baked baking soda.

I know what I am comparing is not exactly equivalent (raising 1 gallon instead of adding solids and making a final volume of 1 gallon), but it should it close enough.

Is the error that large (bulk density measures etc)? or is the calculator wrong? or am I wrong?

[tanya72806]

very interesting I have found this out also I thought maybe I added too much water to one of them and caused them to be balanced out diffrently

[Randy Holmes-Farley]

Is the error that large (bulk density measures etc)? or is the calculator wrong? or am I wrong?

Mostly the former.


Volume is not an especially accurate way to measure solids. The calculator gives the right mass (weight), but it may convert it into volume a bit differently than I did. Dow (and most manufacturers of bulk solids) give a range of bulk densities for the product since the exact volume that a specific mass (say, 500 grams) will occupy depends on many factors, such as the particle size distribution, if it has settled in the measurement, how you pack it, etc. Dow says it ranges from 51 to 60 pounds per cubic foot.

FWIW, there are actually technical reasons why using the calculator beyond its intended purpose is also not completely accurate. If you add a huge amount of Dowflake to water, you actually change the volume and density considerably. I'm sure the calculator does not take that into account, since it is unimportant for changes in reef tanks on the order of 1-500 ppm, but not when you get up into tens of thousands of ppm. My recipe did take the volume change into account, although I should have stated it to be 37,000 mg/L, not ppm (since the density is higher than water with all that Dowflake in it)

As I detail in the recipe article, I assumed a bulk density near the low end. The calculator may not make the same assumption:

http://reefkeeping.com/issues/2006-02/rhf/index.php#20

The Design of the Calcium and Alkalinity Parts

The Dowflake material is supposed to contain 77-80% calcium chloride. From the Dow Flake website, it has a bulk density of 0.82 - 0.96 g/dry mL or 194 - 227 grams/level measuring cup. We will assume that it is 78.5% calcium chloride by weight and weighs 200 grams per level measuring cup. Because calcium comprises 36% of calcium chloride, by weight, each cup contains 200 x 0.785 x 0.36 = 56.5 grams of calcium.

Consequently, dissolving 2 ½ cups (500 g) of Dowflake per gallon = 141 grams of calcium per gallon, or 37,300 mg/L. The final concentration will vary with how much moisture was actually in the calcium chloride, and how well it packed in your measuring cup. A concentration of 37,300 ppm calcium is equivalent to 0.93 molar.

When calcification takes place, two moles of alkalinity are lost for every one mole of calcium. So, we need to match the calcium above with 1.86 molar baking soda (sodium bicarbonate) equivalents (before or after baking, the baking doesn't change the alkalinity). As I measure it, Arm & Hammer baking soda weighs about 264 grams per level measuring cup. Because sodium bicarbonate has a molecular weight of 84 g/mole, we need to dissolve 1.86 x 84 = 156 grams/L, or about 594 grams (2 ¼ level measuring cups) of baking soda per gallon. Note that it doesn't matter how many grams the 594 grams of baking soda becomes after baking. All baking does is change the amount of carbon dioxide and water in the baking soda:

2 NaHCO3 ---> Na2CO3 + H2O + CO2

More, or less, baking will only alter the pH increase upon addition to the aquarium. However, substantial under-baking may make it impossible to fully dissolve the solid material in the recipe, as sodium bicarbonate is less soluble than sodium carbonate (which is why Recipe #2 is more dilute). Overbaking with respect to time or temperature has no negative effect.

[Fraggle Rock2]

Thanks Randy!

One thing I was also assuming is that my measuring cups are actually close to 250mL. I brought them into the lab and determined the mass of water from a level cupful.

I used three different measuring cups and the range was ~211 to 226 g. Overall mean mass was 220g. I measured each cup four times. I used tap water though and it was colder than RT. I don't think that would change the results very much though.

I also measured the mass of 1 cup of MAG pellets, CaCl2 pellets (food grade from two part solutions) and Na2CO3 flakes (food grade from two part solutions) to estimate the bulk densities in g/mL.

For the MAG pellets (measured nine cups - 3 cups from each of 3 different measuring cups) and got a mean bulk density of 0.94g/mL. Mean mass for 1 cup was 206g.

For the CaCl2 pellets (measured three cups, 1 cup from each of the three measuring cups) and got a mean bulk density of 0.89g/mL. Mean mass for 1 cup was 195g.

For the Na2CO3 flakes (measured three cups, 1 cup from each of the three measuring cups) and got a mean bulk density of 0.95g/mL. Mean mass for 1 cup was 208g.

Going to double check the recipes for these materials.

Thanks again!