Alkalinity management

[DGGuaglianone]

Complete novice question but, my tank is currently only consuming alkalinity, no need for calcium or magnesium supplement, water changes are enough to maintain these for now. I currently dose arm and hammer baking soda (sodium bicarbonate, NaHCO3) dissolved in RODI water for my alkalinity supplement. Should I be concerned that I’m adding a significant amount of alkalinity buffer but not balancing it with calcium/magnesium? I’m not worried about specific numbers just trends trying to keep the details out of this discussion. I do test Ca, Mg, nitrate, pH, phosphate, and alkalinity, all are stable except my alkalinity that I’m trying to maintain. Will my tank get out of wack by only dosing alkalinity or is this normal and fine? Thanks for any comment.

 

[Waters]

Complete novice question but, my tank is currently only consuming alkalinity, no need for calcium or magnesium supplement, water changes are enough to maintain these for now. I currently dose arm and hammer baking soda (sodium bicarbonate, NaHCO3) dissolved in RODI water for my alkalinity supplement. Should I be concerned that I’m adding a significant amount of alkalinity buffer but not balancing it with calcium/magnesium? I’m not worried about specific numbers just trends trying to keep the details out of this discussion. I do test Ca, Mg, nitrate, pH, phosphate, and alkalinity, all are stable except my alkalinity that I’m trying to maintain. Will my tank get out of wack by only dosing alkalinity or is this normal and fine? Thanks for any comment.

You will probably get a lot of different answers, but my dosing is controlled by the Apex, and ALK and CA are never dosed equally to maintain the numbers I want to maintain. It is kinda strange you aren't using any CA though (outside of what is replenished with water changes).

 

[bobnicaragua]

I have always done well starting with kalkwasser, and then adding in 2 part once the kalk can’t keep up.

 

[Randy Holmes-Farley]

Complete novice question but, my tank is currently only consuming alkalinity, no need for calcium or magnesium supplement, water changes are enough to maintain these for now. I currently dose arm and hammer baking soda (sodium bicarbonate, NaHCO3) dissolved in RODI water for my alkalinity supplement. Should I be concerned that I’m adding a significant amount of alkalinity buffer but not balancing it with calcium/magnesium? I’m not worried about specific numbers just trends trying to keep the details out of this discussion. I do test Ca, Mg, nitrate, pH, phosphate, and alkalinity, all are stable except my alkalinity that I’m trying to maintain. Will my tank get out of wack by only dosing alkalinity or is this normal and fine? Thanks for any comment.

I think there's a problem in the premise of your question.

The literal answer is that it is OK to dose alk when only alk is depleted, but that only happens if nitrate is constantly rising, and alk is depleted by 2.3 dKH for each 50 ppm rise in nitrate.

Most other situations where folks think calcium is stable are due to calcium moving far more slowly than alk in seawater when both are depleted at the expected ratio of 2.8 dKH alk for each 18-20 ppm calcium. It is easy to detect a 0.5 dKH drop in alk. It is nearly impossible for a reefer to detect the balanced 3 ppm drop in calcium.

Magnesium moves far to slowly to detect by kit for a very long time.

My recommendation is to dose all of alk and calcium and magnesium with a properly balanced additive to maintain alk. A two part or a one part like AFR or kalkwasser (may eventually need some magnesium, or not, depending on the salt mix choice) are good choices.

But if you want to dose just alk, that's fine too, it just puts more pressure on properly monitoring calcium, and when you do need it, you may need to add all of the amount you would have been adding to maintain it in the above plan, but now need to add a larger amount to correct it.

That all said, if you do water changes with a salt mix that has significantly higher alk or calcioum than your tank, that can mess up the expected demand ratios.

 

[wdotero]

I'm in the same situation as DGGuaglianone (thanks for your OP).

My numbers are:
Calcium 410
Magnesium 1470
Alkalinity 7.7

I'd like to have the alkalinity between 8 and 9. Also, I had no idea that nitrate is involved in this balance as well!

My tank is about 6 months old and very recently developed some minor bubble algae. I started adding phytoplankton (for the copepods). This may be related to a rise in the phosphate levels (0.25). Simultaneously, there has been a decrease in nitrate (5). Perhaps it is being used up by the bubble algae?

The fish (clownfish and diamond goby) seem perfectly happy and healthy. The corals are also doing well (torch, xenia, gsp, mushroom).
(Additional info: BioCube 32, salinity 1.025, pH 7.9).

Randy, if you have a moment, I would appreciate your feedback!

Thanks,
Debbie

 

[Randy Holmes-Farley]

Those numbers look fine, but if you want to raise it, most any alk supplement should do.

 

[SomeHappyFish]

I think there's a problem in the premise of your question.

The literal answer is that it is OK to dose alk when only alk is depleted, but that only happens if nitrate is constantly rising, and alk is depleted by 2.3 dKH for each 50 ppm rise in nitrate.

Most other situations where folks think calcium is stable are due to calcium moving far more slowly than alk in seawater when both are depleted at the expected ratio of 2.8 dKH alk for each 18-20 ppm calcium. It is easy to detect a 0.5 dKH drop in alk. It is nearly impossible for a reefer to detect the balanced 3 ppm drop in calcium.

Magnesium moves far to slowly to detect by kit for a very long time.

My recommendation is to dose all of alk and calcium and magnesium with a properly balanced additive to maintain alk. A two part or a one part like AFR or kalkwasser (may eventually need some magnesium, or not, depending on the salt mix choice) are good choices.

But if you want to dose just alk, that's fine too, it just puts more pressure on properly monitoring calcium, and when you do need it, you may need to add all of the amount you would have been adding to maintain it in the above plan, but now need to add a larger amount to correct it.

That all said, if you do water changes with a salt mix that has significantly higher alk or calcioum than your tank, that can mess up the expected demand ratios.

Sorry for hijacking op's thread but I think I'm in a similar situation and I want to make sure I understand correctly how this chemistry works.

My tank has now a lower level of alkalinity (7.21dKH) coming from it's initial start (8dkh) because it got depleted by all kinds of normal biologic cycles, bacteria, algae outbreaks, corals and snails but the calcium and magnesium stayed the same (cal 400pp and mg 1400ppm) because they have been replenished by my weekly water change (10%) but they are in fact being consumed by my inhabitants because most test kit can't detect the balanced 3 ppm drop in calcium or magnesium. A larger difference in calcium or magnesium is easier seen in heavy system with lots of SPS because they are being consumed rather quickly which is not the case of us for now.

Therefor raising the alkalinity backup with a supplement to reach the wanted level is okay but continuing dosing the alkalinity only has a supplement to keep it stable could have an impact later down the road on calcium and magnesium?

Hence the best solution would be:

1. Raise the alkalinity to the wanted level 7.21dkh -> 8dkh (+0.79dKh spread over a day or more)
2. Dose a Alkalinity, calcium and magnesium in the appropriate ratio to keep a healthy chemistry balance on a day to day basis to achieve stable parameters.

This can be achieved with AFR, 2 part, Kalk or else.

Right ?

 

[Bpp124987]

Most people should just dose afr. The powder isn’t over expensive, saves doser heads, and simplifies everything. Dose afr for 8-9 dkh and chill

 

[SomeHappyFish]

Most people should just dose afr. The powder isn’t over expensive, saves doser heads, and simplifies everything. Dose afr for 8-9 dkh and chill

me? or op

 

[Randy Holmes-Farley]

My tank has now a lower level of alkalinity (7.21dKH) coming from it's initial start (8dkh) because it got depleted by all kinds of normal biologic cycles, bacteria, algae outbreaks, corals and snails but the calcium and magnesium stayed the same (cal 400pp and mg 1400ppm) because they have been replenished by my weekly water change (10%) but they are in fact being consumed by my inhabitants because most test kit can't detect the balanced 3 ppm drop in calcium or magnesium. A larger difference in calcium or magnesium is easier seen in heavy system with lots of SPS because they are being consumed rather quickly which is not the case of us for now.

To be clear, the "cycles" is a misnomer. ONLY the production of nitrate from ammonia and calcification by organisms depletes alk in the scenario you describe. There are not other random processes depleting it. Algae do not deplete alk, for example (except Halimeda which has a calcium carbonate structure inside).

But yes that you won't detect the calcium or magnesium drops associated with a 1 dKH drop in alk, no matter what is causing it. I'd always dose balanced alk and calcium, but when demand is low, you can wait on the calcium until you see a need).

Yes to your final question.

 

[Randy Holmes-Farley]

Most people should just dose afr. The powder isn’t over expensive, saves doser heads, and simplifies everything. Dose afr for 8-9 dkh and chill

Why?

I can think of multiple reasons why other methods may be better.

AFR is often a fine choice, but it is not a standout better choice. Other methods can help boost pH, can allow adjusting calcium dosing relative to alkalinity dosing, are cheaper, and may be easier to automate.

 

[SomeHappyFish]

Thank you for clarifying.

I might go with 2 part, ESV-B ionic, I can raise alk, with very little calcium at first then adjuste from there and also gain a slight ph boost.

AFR looks great but doesn't seem to be a right fit at the moment, I don't need to replenish mg and trace elements, my water change takes care of it.

 

[Bpp124987]

Why?

I can think of multiple reasons why other methods may be better.

AFR is often a fine choice, but it is not a standout better choice. Other methods can help boost pH, can allow adjusting calcium dosing relative to alkalinity dosing, are cheaper, and may be easier to automate.

The persona I have in mind for that recommendation is someone that newer to the hobby, or doesn’t have the time to evaluate all those options nor grasp the nuances of implementation.

 

[Randy Holmes-Farley]

The persona I have in mind for that recommendation is someone that newer to the hobby, or doesn’t have the time to evaluate all those options nor grasp the nuances of implementation.

I don’t have a problem with it being described as a good choice, either for new reefers or in general for smaller tanks.

 

[Bpp124987]

I don’t have a problem with it being described as a good choice, either for new reefers or in general for smaller tanks.

Works great in my 200 gallon mixed reef too.

I’ve done kalk, multi part including balling method, etc. before the powder came out it would’ve been prohibitively expensive, but with the powder you save money in additional dosing heads etc. I repurposed and entire Dos to do auto water changes when switching from balling to afr. Only have to mix up and refill one container…. Seriously, the stuff is great.