2 part dosing Ca, holding Alk

t5Nitro · Apr 27, 2020

Is it unusual or not recommended to 2-part dosing (1 part dosing) Ca and not Alkalinity? I'm still letting my numbers fall a bit. Ca was 425 today with Alk at 8.4 dKh. I'd like for Ca to maintain around this number, and alkalinity to continue to drop to around 8.

I hadn't dosed 2 part in quite a while now, but today Calcium hit 425 and figured I'd give it a dose without any alkalinity at this time.

dwest · Apr 27, 2020

You can dose just calcium for now.

Randy Holmes-Farley · Apr 28, 2020

If you are not adding either calcium or alkalinity, and let alkalinity fall by 0.4 dKH, calcium will only fall by about 2.7 ppm.

That drop cannot be detected with a hobby kit and will keep you where you want calcium.

That said, if it concerns you, you can also dose the tiny amount needed.

t5Nitro · Apr 28, 2020

Is it reasonable to use the BRS calculator to raise my Ca from 417 to 420ppm (this value keeps my balanced alk at 8.0 dKh) requiring 3.1g, or 0.6tsp to make a solution? Wiki is telling me solubility of anhydrous CaCl2 is 74.5g/100mL. Should be able to roughly dissolve the full 3.1g into 4mL of water to get that dose. If that were the case at 4mL daily, 600mL solution would be a 5 month supply. Seems like at some point I would need to increase the dose of course.

Randy Holmes-Farley · Apr 28, 2020

t5Nitro said:
Is it reasonable to use the BRS calculator to raise my Ca from 417 to 420ppm (this value keeps my balanced alk at 8.0 dKh) requiring 3.1g, or 0.6tsp to make a solution? Wiki is telling me solubility of anhydrous CaCl2 is 74.5g/100mL. Should be able to roughly dissolve the full 3.1g into 4mL of water to get that dose. If that were the case at 4mL daily, 600mL solution would be a 5 month supply. Seems like at some point I would need to increase the dose of course.

That seems an extraordinarily specific target calcium range. nothing will be detectably different at 400 or 475 ppm calcium.

You can dissolve calcium chloride to about any concentration you want. if you use one of my recipes, there will be calculator entries for the solution, but the one below also has the dry additive entry:

This calculator may be easier to use:

Reef Chemistry Calculator

t5Nitro · Apr 28, 2020

I'm using BRS sodium carbonate and calcium carbonate dihydrate. I had to look up your recipes which must be where this stuff came from because it's essentially the same. The amount mixed into 1 gallon is a bit more concentrated than in your recipe #2. I can use that calculator in the link and dose a smaller volume than recommended and re-test when I get to needing to increase alk.

Randy Holmes-Farley · Apr 28, 2020

t5Nitro said:
I'm using BRS sodium carbonate and calcium carbonate dihydrate. I had to look up your recipes which must be where this stuff came from because it's essentially the same. The amount mixed into 1 gallon is a bit more concentrated than in your recipe #2. I can use that calculator in the link and dose a smaller volume than recommended and re-test when I get to needing to increase alk.

Yes, BRS uses my recipes.

t5Nitro · Apr 28, 2020

Thanks, Randy. Will go ahead and use that calculator for your recipe #2 and go from there with some trials and testing. Appreciate your presence in this hobby.

Randy Holmes-Farley · Apr 28, 2020

The BRS recipe using sodium carbonate is my Recipe #1.

t5Nitro · Apr 28, 2020

So if I were to bake 2.25 cups of baking soda or sodium bicarb, then I should end up with approximately 1 cup of sodium carbonate at the end? Just looking at the equation and seeing where brs recipe comes out to 1 cup soda ash per gallon as opposed to 2.25 cups baking soda.

Randy Holmes-Farley · Apr 28, 2020

t5Nitro said:
So if I were to bake 2.25 cups of baking soda or sodium bicarb, then I should end up with approximately 1 cup of sodium carbonate at the end? Just looking at the equation and seeing where brs recipe comes out to 1 cup soda ash per gallon as opposed to 2.25 cups baking soda.

No.

There are two recipes, and BRS provides chemicals for both. Using soda ash (sodium carbonate), the BRS recipe (my recipe 1) is

"Fill a 1-gallon container 4/5 full of RO/DI or distilled water and then add 2 1/3 cups of BRS Pharma Soda Ash into the container. "

BRS adjusts their volume-based version of my recipe to match the sodium carbonate they sell. Different manufacturers of the same chemical may provide it in different bulk densities (that is, fluffiness).

t5Nitro · Apr 28, 2020

Ahh gottcha. That's tough to mix your own if not sure the amount of fluff or air in the particle. Will stick with whatever the current mix I have recommends =)

Randy Holmes-Farley · Apr 28, 2020

t5Nitro said:
Ahh gottcha. That's tough to mix your own if not sure the amount of fluff or air in the particle.

My recipes have weights, so if you have a scale and are using a different brand than I suggest, you can check it.

t5Nitro · Apr 28, 2020

The volumes threw me off because a fellow hobbiest recommended mixing 2 dry cups soda ash to 1/2 gallon of water to make a more concentrated solution. He was dosing up to 40mL daily of this. So in the past 2 months when I had my alk spike it isn't a surprise that it went to 11.9 after which I d/c the dosing pump and stopped dosing 2-part altogether. It just now is getting to low-mid 8s.

Somewhere I thought I read the BRS mixing instructions was 1 cup 2 T to 1 gallon of RODI water. Now that I look again I see it's 2 1/3 c. Either way I'm nearly double their recommended dose. With your recipe recommendations starting at 0.5ml/gallon on my ~90 gallon system I probably should be at no more than 22ml daily. I think I was up to 40ml daily at one point. Even after trying to reduce the volume my alk would still climb at 10ml/daily.

So I guess I don't know what concentration I ended up making but it looks like probably that I was dosing twice what I should have been to start.

Randy Holmes-Farley · Apr 28, 2020

I fixed the recipe concentration based on the difficulty if dissolving it all. It would be quite hard, I think, to double my recipe concentration since that is near the actual limit.

t5Nitro · Apr 28, 2020

2 cups brs soda ash will dissolve fully into 1/2 gallon of water. Its sitting in my basement. Yes, you shake a lot.

Randy Holmes-Farley · Apr 28, 2020

t5Nitro said:
2 cups brs soda ash will dissolve fully into 1/2 gallon of water. Its sitting in my basement. Yes, you shake a lot.

Not if it gets cold. lol

the solubility drops off fast at lower temperatures.
Solubility
g/100 mL:

7 (0 °C)
16.4 (15 °C)
34.07 (27.8 °C)
48.69 (34.8 °C)

You dissolved to a concentration of about 20 g/100 mL.

that is why I did not make the recipe more concentrated: it is hard to dissolve and will precipitate out if it gets cool.

t5Nitro · Apr 28, 2020

If I mix a new solution to the appropriate recipe, what should I be doing on paper to find the number of mL required to raise 284L by 0.1 dKh?

At a concentration of 10g/100ml it comes to 19,845dkh/3780ml or 5.25dkh per ml.

The reef calculator let's me put in 8.1 with goal 8.2 dkh and spits out 5.3mL.

Just curious on how I go calculate it myself so it's more than an online calculator.

Randy Holmes-Farley · Apr 29, 2020

t5Nitro said:
If I mix a new solution to the appropriate recipe, what should I be doing on paper to find the number of mL required to raise 284L by 0.1 dKh?

At a concentration of 10g/100ml it comes to 19,845dkh/3780ml or 5.25dkh per ml.

The reef calculator let's me put in 8.1 with goal 8.2 dkh and spits out 5.3mL.

Just curious on how I go calculate it myself so it's more than an online calculator.

Sure.

My recipe #1 is 5,300 dKH.

"This solution will contain about 1,900 meq/L of alkalinity (5,300 dKH). "

If you want to boost aquarium water by Z dKH using Y mL , you just do a dilution calculation:

Z dKH = 5300 dKH x Y mL/(tank volume in mL)

As an example, let Z be 1 dKH (that is, you want a 1 dKH rise) and the tank volume is 100 gallons ( 378,541 mL)

1 dKH = 5,300 dKH x Y/(378,541 mL)

Y = 71.4 mL

FWIW, dKH per mL is not a correct unit. It is just dKH, which already has a volume element buildt in.

t5Nitro · Apr 30, 2020

Thanks!

I'm not sure what crazy math I was doing to get those numbers above. I think I have it down now and getting the same numbers using your recipe #1 594g sodium bicarb with valence of 1, and using 378g sodium carbonate with valence of 2.

I took 378g Na2CO3 = [378,000mg Na2CO3 / 106 mg/mmol] x 2 (valence) --> 7132 mEq / 3.78L ~~1900mEq/L, or about 5300dKh.

I appreciate the help, and hopefully some folks a lot smarter than me got a kick out of some of that. I was eager to remember how to do these calculations so that I can take it over to trisodium phos and sodium nitrate and feel like I have a better grasp of what I'm actually doing when I'm dosing. Thanks!