Balancing Alkalinity after prolonged Kalkwasser usage

[Dennis Cartier]

The effect on pH will be negligible as it is such a small amount.

Recently there have been discussions (on R2R) about using KOH to boost pH. That is not what I am attempting here. Frankly the idea of using KOH solely for pH support is nonsensical (in my view) as it has such a narrow range of acceptable levels, and elevating it too high will bring possible repercussions.

The average person should just use potassium chloride as Randy suggests. It is available in retail products and is safe and easy to administer when dosed appropriately.

 

[Cybernation]

The effect on pH will be negligible as it is such a small amount.

Recently there have been discussions (on R2R) about using KOH to boost pH. That is not what I am attempting here. Frankly the idea of using KOH solely for pH support is nonsensical (in my view) as it has such a narrow range of acceptable levels, and elevating it too high will bring possible repercussions.

The average person should just use potassium chloride as Randy suggests. It is available in retail products and is safe and easy to administer when dosed appropriately.

Hi - I currently use kalk slurry. I’m maintaining a ph of 8.3-.4. Without the use of slurry, I cannot get it above 7.95. Can you please go into the repercussions? If you have an automated system, with safe guards for alk levels, and ph levels, where are the risks? I have 2 big wave makers in my sump in the basement, and a mixing pump in my kalk container. I’ve accidentally left one pump off in my sump, nothing happened. If the pump dies in the kalk container, the only thing that could happen is my alk will drop like a rock. I have a demand of approx 2dkh to 2.5dkh. I do water changes of 20-35 gals every 2-3 weeks…

 

[Dennis Cartier]

Hi - I currently use kalk slurry. I’m maintaining a ph of 8.3-.4. Without the use of slurry, I cannot get it above 7.95. Can you please go into the repercussions? If you have an automated system, with safe guards for alk levels, and ph levels, where are the risks? I have 2 big wave makers in my sump in the basement, and a mixing pump in my kalk container. I’ve accidentally left one pump off in my sump, nothing happened. If the pump dies in the kalk container, the only thing that could happen is my alk will drop like a rock. I have a demand of approx 2dkh to 2.5dkh. I do water changes of 20-35 gals every 2-3 weeks…

Actually that post is about Potassium Hydroxide, not Calcium Hydroxide.

That being said, I have a different set of concerns about dosing a kalk slurry. Obviously you touched on the need for safeguards, because a little oops moment when dealing something like a kalk slurry will become a significant problem fast.

My actual concern is the purity of the kalk you use in your slurry. You would want to be very careful about the kalk you purchase to use for this purpose. The reason is that most kalk gets used as a settled clear liquid, and the kalkwasser will self purify by precipitating the impurities from the high pH level. But if you are dosing a kalk slurry, you are dosing everything, impurities and all. So making sure there are little if any impurities becomes important.

I would suggest watching the BRS video on testing kalk purity. They don't give the brand names they are testing, but some of them clearly contain significant impurities.

You being in Canada, howdy neighbour, the BRS Pharma grade is not easy to get. I have some from SR Aquaristiks, which you can buy from Amazon, that claims to be Pharma grade, but is it? I don't know, maybe, but it could just as easily be another brand white labelled.

 

[Cybernation]

Actually that post is about Potassium Hydroxide, not Calcium Hydroxide.

That being said, I have a different set of concerns about dosing a kalk slurry. Obviously you touched on the need for safeguards, because a little oops moment when dealing something like a kalk slurry will become a significant problem fast.

My actual concern is the purity of the kalk you use in your slurry. You would want to be very careful about the kalk you purchase to use for this purpose. The reason is that most kalk gets used as a settled clear liquid, and the kalkwasser will self purify by precipitating the impurities from the high pH level. But if you are dosing a kalk slurry, you are dosing everything, impurities and all. So making sure there are little if any impurities becomes important.

I would suggest watching the BRS video on testing kalk purity. They don't give the brand names they are testing, but some of them clearly contain significant impurities.

You being in Canada, howdy neighbour, the BRS Pharma grade is not easy to get. I have some from SR Aquaristiks, which you can buy from Amazon, that claims to be Pharma grade, but is it? I don't know, maybe, but it could just as easily be another brand white labelled.

Lol hey hey eh!. I am using the sr stuff. I can’t source anything cheaper. I did get a quote for Pharma grade but it was more expansive than the aquaristiks. I did see the brs video on impurities I don’t believe everything they say. Ill be doing an icp in the next few weeks just to be sure.

 

[Randy Holmes-Farley Verified Community Expert]

The other concern with a slurry is the possibility of undissolved calcium hydroxide landing on something delicate.

You must have relatively low evaporation to need a slurry to dose 2-2.5 dKH per day.

Evaporation of 2.2% daily will give you 2.5 dKH per day..

 

[nereefpat]

Evaporation of 2.2% daily will give you 2.5 dKH per day..

Is evaporation of 2.2% common? That would be about 2 gallons for a 90 gallon tank. I saw about half that in my 90 gallon. Now about 1.5 gallons in my 125 + 40 sump. Of course it depends on temperatures of air and water, and humidity, and surface area. That just seems like a lot to me. I estimate that much over about 1 dKH per day is approaching the limits of straight kalk.

 

[Randy Holmes-Farley Verified Community Expert]

Is evaporation of 2.2% common? That would be about 2 gallons for a 90 gallon tank. I saw about half that in my 90 gallon. Now about 1.5 gallons in my 125 + 40 sump. Of course it depends on temperatures of air and water, and humidity, and surface area. That just seems like a lot to me. I estimate that much over about 1 dKH per day is approaching the limits of straight kalk.

Guess it depends on skimmers, sumps, refugia, humidity, etc. My evaporation was often 2+% daily.

 

[Dennis Cartier]

For me it depends on the season. In wintertime, having a set amount of kalk added through a dosing pump, still requires my ATO to periodically top up. Fast forward to summertime, and the same dosing schedule is so close to my evaporation rate that the diluted LaCl that I was adding through my Lanthanum reactor caused me to over run my evaporation rate. So time of year and local environment has a big effect in my experience.

 

[Lividfanatica]

Using KOH is far more likely to result in an imbalance than is sodium hydroxide (or carbonate/bicarbonate) because there is 26x more sodium to begin with.

KOH is 70% potassium.

Sorry, Randy, I am confused. I too am looking for a way to bump up Alk without CA (I like your idea of switching to high alk/low CA salt mix and using Kalkwasser), and KOH seemed like a good option to me. I plan on running zeovit which results in reduced K.

Is your primary concern with KOH "imbalancing" the tank due to the amount of K? I am guessing the single hydroxide on KOH vs two on CA(OH)2 results in a much lower ALK boost, but would it be enough? Any idea on the ratio of K to Alk? say 50 ppm of K would be equal to .5 dkh or something (making that up as an example). Obviously, K would be the limiting factor to dosing this daily, but would it work for a correction (to both K and Alk) on occasion?

I appreciate all you do for the community! Thanks in advance!

 

[Randy Holmes-Farley Verified Community Expert]

Sorry, Randy, I am confused. I too am looking for a way to bump up Alk without CA (I like your idea of switching to high alk/low CA salt mix and using Kalkwasser), and KOH seemed like a good option to me. I plan on running zeovit which results in reduced K.

Is your primary concern with KOH "imbalancing" the tank due to the amount of K? I am guessing the single hydroxide on KOH vs two on CA(OH)2 results in a much lower ALK boost, but would it be enough? Any idea on the ratio of K to Alk? say 50 ppm of K would be equal to .5 dkh or something (making that up as an example). Obviously, K would be the limiting factor to dosing this daily, but would it work for a correction (to both K and Alk) on occasion?

I appreciate all you do for the community! Thanks in advance!

Bump alk and not calcium is extraordinarily easy.

Sodium bicarbonate (baking soda) sodium carbonate (washing soda), sodium hydroxide (lye), or any reef company alk additive.

There's never any reason to use KOH for this purpose. It's a very strange suggestion, IMO, and not worthy of consideration. The concern over KOH is that you will boost potassium, regardless of whether the tank needs it or not. KOH is 70% potassium by weight, and adding 1 meq/L (2.8 dKH )will boost potassium by 39 ppm.

Sodium hydroxide is a far better choice in almost every respect. Any rise to Na+ is lost in the vast concentration of sodium in seawater (>10,000 ppm) and NaOH is only 41% sodium by weight.

If one needs to raise K+ (I never needed to in 20 years), food grade potassium chloride is appropriate and inexpensive.

 

[Lividfanatica]

Bump alk and not calcium is extraordinarily easy.

Sodium bicarbonate (baking soda) sodium carbonate (washing soda), sodium hydroxide (lye), or any reef company alk additive.

There's never any reason to use KOH for this purpose. It's a very strange suggestion, IMO, and not worthy of consideration. The concern over KOH is that you will boost potassium, regardless of whether the tank needs it or not. KOH is 70% potassium by weight, and adding 1 meq/L (2.8 dKH )will boost potassium by 39 ppm.

Sodium hydroxide is a far better choice in almost every respect. Any rise to Na+ is lost in the vast concentration of sodium in seawater (>10,000 ppm) and NaOH is only 41% sodium by weight.

If one needs to raise K+ (I never needed to in 20 years), food grade potassium chloride is appropriate and inexpensive.

Thank you very much! Recently I was K deficient and needed quite a bit to get back to "normal" levels (400-420ppm). I'll go the NaOH route and use KCl for any K adjustments.

 

[Randy Holmes-Farley Verified Community Expert]

Thank you very much! Recently I was K deficient and needed quite a bit to get back to "normal" levels (400-420ppm). I'll go the NaOH route and use KCl for any K adjustments.

You're welcome.

FWIW, here's a good food grade KCl:

NOW Foods, Potassium Chloride Powder, 8 oz (227 g)

www.iherb.com

Happy reefing.