Balance Dosing?

Kenmx10 · Nov 9, 2015

Hi Randy, Regarding dosing Alkalinity and Calcium, it is understood that they should be balanced when dosing. My question is: With a 200 gallon tank, ( lets say 200 gallons total water volume for the sake of discussion), where the calcium is at 420 and the alkalinity is at 6.8, would adding 16 oz of 2 part (sodium carbonate) to bring the Alkalinity up to eight be considered a balanced dose being that the calcium is already where it needs to be? Or would it be considered unbalance because no calcium was added with the sodium carbonate?

Randy Holmes-Farley · Nov 9, 2015

That single one time dose is fine, but equal parts dosing would only bring the calcium to about 429 ppm from 420 ppm, which is also fine.

Kenmx10 · Nov 9, 2015

Thx Randy. I have one more question. I can't keep my calcium and alkalinity needs up using Kalk only, due to slower evaporation rates. So a couple times a week I have to dose using BRS 2 part, to keep up. Usually I have more problems keeping the alkalinity up than the calcium. Can I check my alkalinity dosing needs and just match my calcium accordingly? For instance, if I need to add 10 ounces soda ash, is there an equivalent amount of calcium chloride that I can add to match the alkalinity? (So many ounces of calcium chloride to so many ounces of sodium carbonate). Or should I just keep adjusting them separately? The reason I ask it that lately for some reason my calcium and alkalinity have been getting farther apart and the more individual adjustments I made, the farther apart they would get. I finally got things stabilized and back to normal, and and am looking for a more balance way of dosing to prevent the swings from happening again in the future. Thanks for your help!

Randy Holmes-Farley · Nov 10, 2015

The primary reason some people use unbalanced dosing is because they use a salt mix that doesn't match their tank in terms of calcium and alkalinity. So their dosing is constantly adjusting for the water changes and/or the starting concentrations.

IMO, the exact calcium level seems to be fairly unimportant in the range from 400 to 550 ppm, so unless calcium is too high (above 550 ppm), there's really not that much reason to do anything except equal parts dosing based on the alkalinity demand. That said, if you want to for some reason, and are willing to measure calcium more frequently, it is fine to do so. It just eliminates one of the advantages of a two part (that you can essentially go with rarely measuring calcium), and frankly, is not needed as often as folks seem to think. IMO, it is a case of, if they can tweak it, they will. People using dosing pumps seem to be especially prone to this need to tweak.

Folks using limewater (kalkwasser) or a CaCO3/CO2 reactors cannot make such uneven doses, and usually don't seem to feel the need.

I give the balanced amounts in this article with my DIY two part recipe:

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

Note that for this purpose, 594 grams of baking soda (sodium bicarbonate) is equivalent in alkalinity to 375 grams of washing soda (sodium carbonate).

Finally, alkalinity swings up and down a lot faster on a percentage basis than does calcium when over or under dosing, so it is often the first indicator that you need to adjust dosing, and possibly of both. For example, if you start at 8 dKH and 430 ppm calcium, then let corals do their thing, the new values could be 6 dKH and 413 ppm, which seems like the alk dropped a lot and the calcium not so much, but that is just the math of the ratio that corals use, and you need equal parts dosing to correct it back to the starting point.

d_adler · Nov 10, 2015

In my case I tried balanced dosing in my 50gal (I would say 40gal water volume total) but the calcium always drops down to like 350ppm even though my alk is staying between 8-8.5dkh at 35ml a day

Randy Holmes-Farley · Nov 10, 2015

d_adler said:
In my case I tried balanced dosing in my 50gal (I would say 40gal water volume total) but the calcium always drops down to like 350ppm even though my alk is staying between 8-8.5dkh at 35ml a day

What were you dosing?

What salt mix and salinity?

d_adler · Nov 10, 2015

Sodium Carbonate for alk and Calcium Chloride calcium. I was using Red Sea pro with the same problem but now I'm using natural sea water

d_adler · Nov 10, 2015

Randy Holmes-Farley said:
What were you dosing?

What salt mix and salinity?

Salinity crept up up on me and is 1.029 right now

Randy Holmes-Farley · Nov 10, 2015

d_adler said:
Sodium Carbonate for alk and Calcium Chloride calcium. I was using Red Sea pro with the same problem but now I'm using natural sea water

Are you using my DIY recipe (the BRS recipe) for the ratio of sodium carbonate to calcium chloride?

d_adler · Nov 10, 2015

Randy Holmes-Farley said:
Are you using my DIY recipe (the BRS recipe) for the ratio of sodium carbonate to calcium chloride?

Not that I'm aware of. I was on the losing side of a war against parameters until my alk stabilized about a month ago

Randy Holmes-Farley · Nov 10, 2015

d_adler said:
Not that I'm aware of. I was on the losing side of a war against parameters until my alk stabilized about a month ago

Then how do you know that dosing a balanced ratio does not work for you?
In other words, how do you know you were dosing a balanced ratio when the calcium declined to 350 ppm?

d_adler · Nov 10, 2015

I didn't understand what a balanced ratio was then.
I thought a balanced ratio referred to an equal amount of both alk and ca dosed but I am wrong.
How would I find out what a balanced dose is?
I'm currently dosing 32ml of alk with it stable while dosing 37ml of ca and it continues to drop

d_adler · Nov 10, 2015

Randy Holmes-Farley said:
Then how do you know that dosing a balanced ratio does not work for you?
In other words, how do you know you were dosing a balanced ratio when the calcium declined to 350 ppm?

Oceansize · Nov 10, 2015

@d_adler: if you're adding Calcium and finding that your Calcium is not rising as expected, it could very well be because your Magnesium is too low. You have to have enough Magnesium present in order for the calcium dosing to have the desired effect. Magnesium should be at least 1320.

Randy Holmes-Farley · Nov 10, 2015

Balanced dosing does not mean equal amounts of solids.

It means dosing calcium and alkalinity in the same proportions that corals use them to deposit calcium carbonate skeletons. Some methods naturally dose only this ratio, such as limewater/kalkwasser, and CaCO3/CO2 reactors. Equal parts dosing of a properly designed two part system also adds things in this ratio.

A balanced ratio is about 18-20 ppm calcium for each 1 meq/L (2.8 dKH) of alkalinity.

In terms of calcium chloride dihydrate and sodium carbnonate, that turns out top be about 500 grams of the calcium additive to 375 grams of the sodium carbonate.

If you were dosing equal amounts of solids in an amount to maintain alkalinity, then one would expect calcium to steadily decline, as you observed.

FWIW, I discuss the DIY two part recipes here:

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

Randy Holmes-Farley · Nov 10, 2015

Oceansize said:
@d_adler: if you're adding Calcium and finding that your Calcium is not rising as expected, it could very well be because your Magnesium is too low. You have to have enough Magnesium present in order for the calcium dosing to have the desired effect. Magnesium should be at least 1320.

It would not cause calcium to decline and alkalinity to be stable, however. They have to decline together (or be supplemented together) for precipitation of calcium carbonate to be a sink for calcium,. In fact, for calcium to decline from 420 to 350 ppm, alkalinity would have to decline by about 10 dKH.

Kenmx10 · Nov 10, 2015

Muchas Gracias Randy!

Randy Holmes-Farley · Nov 10, 2015

Kenmx10 said:
Muchas Gracias Randy!

You're welcome.

Happy Reefing.

d_adler · Nov 10, 2015

Randy Holmes-Farley said:
Balanced dosing does not mean equal amounts of solids.

It means dosing calcium and alkalinity in the same proportions that corals use them to deposit calcium carbonate skeletons. Some methods naturally dose only this ratio, such as limewater/kalkwasser, and CaCO3/CO2 reactors. Equal parts dosing of a properly designed two part system also adds things in this ratio.

A balanced ratio is about 18-20 ppm calcium for each 1 meq/L (2.8 dKH) of alkalinity.

In terms of calcium chloride dihydrate and sodium carbnonate, that turns out top be about 500 grams of the calcium additive to 375 grams of the sodium carbonate.

If you were dosing equal amounts of solids in an amount to maintain alkalinity, then one would expect calcium to steadily decline, as you observed.

FWIW, I discuss the DIY two part recipes here:

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

So if I was dosing 32ml with a steady 8dkh then I should dose (1.3 times ca) around 42 ml?

Randy Holmes-Farley · Nov 10, 2015

d_adler said:
So if I was dosing 32ml with a steady 8dkh then I should dose (1.3 times ca) around 42 ml?

Yes, that's a reasonable ratio to try, but I'd manually correct the calcium with some bigger doses over 2-3 days.

This shows how much would be needed:

http://reef.diesyst.com/chemcalc/chem_calc3.html