kalkwasser and high alkalinity

[mattzang]

hello, so about two weeks ago I started doing kalkwasser in my ATO container. I started with 3 teaspoons to about 4 gallons of RODI. slightly more than the 1/2 teaspoon per gallon, but i have a bunch of corals in my tank and i had been dosing bionic 2 part at about 6 ml/s a day. after my last water change (plus starting kalkwasser) i noticed my alk had jumped from about mid 8s to about high 9s, so i stopped dosing the two part. i got busy this week and from when i last tested (high 9s monday) to this morning my alk is now 11.8 , so i added a couple gallons of RODI to my ATO without any kalk. so uhh, my question is, what the heck?!? do i even try doing 1/2 teaspoon per RODI gallon or is my tank just not eating up enough alk to do kalk?

also, i don't have an apex or anything to monitor pH, but i tested that this morning and it was somewhere between the 8.4 and the 8.6 on a salifert test (this was before my lights even went on). how accurate are those tests and how bad is a pH that high? is there some way to do kalk without it jacking my pH up that high? I won't lie, i rarely ever tested pH before i was doing kalk because short of opening doors and windows and running a refugium i didn't really have a way to mess with it so i didn't test and left it alone. before doing kalk i tested it a few times at different times of the day and it was generally in the 7.9/8.0ish range, so i figured i could do better there.

should i just dump out my ATO container and go back to dosing 2 part? i have had some coral issues lately, but i also recently got into trying to do acros, so i kinda chalked that up to just not knowing what i'm doing with them yet. issues including RTN of one acro, STN of another, and just recently my strawberry shortcake looked like it bleached, but not like RTN. it was fast (overnight), but didn't look bleach white like the RTN one did, but definitely lost color and looks like better days might not be ahead.

oh and last parameters check:

alk today: 11.8
calcium last weekend: 419
magnesium a couple weeks ago: 1380
nitrates 10~
phosphates were .04 a couple weeks ago
temp: 78-80

 

[Justfebreezeit]

When I started kalk it was at the ratio of 1 tsp to 5 gallons. So if you want to use kalk just keep adjusting it till it hits where you need it do be.

 

[desagon]

I had the same thing happen to me recently when I added kalk to my ato. I have always added 3 teaspoons to 4 gallons, and my dkh was always between 8-9 and ph was always 8.1-8.2. For some reason though, my alkalinity skyrocketed to nearly 12 dkh recently and I have stopped adding kalk to my ato. At least until it subsides and i can figure out what happened. So im interested in what others have to say about this as well.

 

[Hemmdog]

Why did you switch to kalk from 2 part ? I’d just go back to 2 part because now your alk and cal are out of balance. You need some cal in there. Kalk makes pH very high and dosing something that messes with your parameters depending on water evaporation rate is insanity imo.

 

[Mical]

It all depends on how you add kalk. If you dump it in ato and stir lightly it blends with ATO/RODI water better than mixing it alot (according to BRS) you don't get a surge of kalk. I always did 1 tsp per gallon then test after a week. Eventually dropped to 1/2 tsp per gallon. Since switching to HW Marinemix Reefer salt, I don't add any kalk to ATO and levels are dang near spot on.

 

[mattzang]

Why did you switch to kalk from 2 part ? I’d just go back to 2 part because now your alk and cal are out of balance. You need some cal in there. Kalk makes pH very high and dosing something that messes with your parameters depending on water evaporation rate is insanity imo.

kalk adds calcium too

https://www.bulkreefsupply.com/instructions/article/using-kalkwasser

that reminds me tho i need to test calcium i'm guessing that's a lot higher too

 

[mattzang]

I had the same thing happen to me recently when I added kalk to my ato. I have always added 3 teaspoons to 4 gallons, and my dkh was always between 8-9 and ph was always 8.1-8.2. For some reason though, my alkalinity skyrocketed to nearly 12 dkh recently and I have stopped adding kalk to my ato. At least until it subsides and i can figure out what happened. So im interested in what others have to say about this as well.

hmm, do you use the BRS kalk? idk if that has anything to do with it, maybe it's super potent or something? lol

 

[desagon]

I do use BRS kalk and I have been using it for over a year. Have you changed salt brands or anything? @Mical brought up a good point. I recently switched over to HW reefer salt and thats when I noticed my alk levels near 12.

 

[mattzang]

I do use BRS kalk and I have been using it for over a year. Have you changed salt brands or anything? @Mical brought up a good point. I recently switched over to HW reefer salt and thats when I noticed my alk levels near 12.

I use IO salt, reef crystals and the standard one i mix them up. the alk is pretty high for IO, but i only do 5 or 10 gallon water changes once every 2 weeks and i've never tested my alk where it was anywhere over 10 before

 

[sghera64]

Why did you switch to kalk from 2 part ? I’d just go back to 2 part because now your alk and cal are out of balance. You need some cal in there. Kalk makes pH very high and dosing something that messes with your parameters depending on water evaporation rate is insanity imo.

Kalk [ Ca(OH)2 ] has the result of adding calcium and alkalinity in the correct balanced proportions. It alone should not throw off your alkalinity.

 

[Hemmdog]

Kalk [ Ca(OH)2 ] has the result of adding calcium and alkalinity in the correct balanced proportions. It alone should not throw off your alkalinity.

How can there be such a thing as correct balanced proportions when different corals consume different elements are different rates? Kalk also doesn’t supplement magnesium that is included in the calcium component in 2part.

 

[mattzang]

tested calcium and it's highish too, but not scary high: 469

oh and i was mistaken earlier alk was 11.2 not 11.8, still quite a bit higher than i was aiming for lol

gonna do a water change i guess. not sure that will do anything since my salt is high levels anyway, but it's my equivalent of restarting the computer when it's broken. tank broken? water change. computer broken? restart.

 

[sghera64]

How can there be such a thing as correct balanced proportions when different corals consume different elements are different rates? Kalk also doesn’t supplement magnesium that is included in the calcium component in 2part.

I was referring to adding Ca and Alk in the same proportion taken up by stony corals when they make CaCO3 skeletal matter. One Ca(OH)2 adds one Ca and ‘effectively’ one CO3 (-2) after the 2 OH- do their part reacting with CO2 in the system.

You are correct in that Kalk adds no other species including not adding Mg.

 

[Dkeller_nc]

A few notes -

It doesn't matter how much kalk powder you add to RODI if it's over about 1/2 teaspoon per gallon. Calcium hydroxide (kalk powder) has a low solubility in water, and so anything over 1/2 teaspoon per gallon will simply settle out to the bottom of the mixing container.

Saturated kalkwasser is not very "strong" in terms of adding alkalinity and calcium to your tank. In fact, for most tanks with a reasonable amount of growing corals and coralline algae, it won't keep up with alkalinity/calcium demand, even with relatively high evaporation rates.

When I see posts describing a problem like this - an alkalinity spike, it's typically caused by someone adding a large amount of kalk powder directly to an ATO reservoir. While the amount of kalk delivered to the tank in the makeup water itself will be fairly low, the typical issue is that the ATO pump is pulling undissolved kalk powder from the bottom of the reservoir and adding it to the tank. Under those circumstances, it's possible to add a great deal of alkalinity to a tank in a very short amount of time.

Bottom line - if you choose to use saturated kalkwasser as a supplement to your alkalinity additions through an ATO, it's important to measure your alkalinity demand and your evaporation and determine whether saturated kalkwasser is going to "over do it". And, if you determine that kalkwasser makes sense, it's important to mix the kalk powder in a separate container and then pour only the clear liquid into your ATO to prevent directly adding kalk powder to your tank.

 

[mattzang]

A few notes -

It doesn't matter how much kalk powder you add to RODI if it's over about 1/2 teaspoon per gallon. Calcium hydroxide (kalk powder) has a low solubility in water, and so anything over 1/2 teaspoon per gallon will simply settle out to the bottom of the mixing container.

Saturated kalkwasser is not very "strong" in terms of adding alkalinity and calcium to your tank. In fact, for most tanks with a reasonable amount of growing corals and coralline algae, it won't keep up with alkalinity/calcium demand, even with relatively high evaporation rates.

When I see posts describing a problem like this - an alkalinity spike, it's typically caused by someone adding a large amount of kalk powder directly to an ATO reservoir. While the amount of kalk delivered to the tank in the makeup water itself will be fairly low, the typical issue is that the ATO pump is pulling undissolved kalk powder from the bottom of the reservoir and adding it to the tank. Under those circumstances, it's possible to add a great deal of alkalinity to a tank in a very short amount of time.

Bottom line - if you choose to use saturated kalkwasser as a supplement to your alkalinity additions through an ATO, it's important to measure your alkalinity demand and your evaporation and determine whether saturated kalkwasser is going to "over do it". And, if you determine that kalkwasser makes sense, it's important to mix the kalk powder in a separate container and then pour only the clear liquid into your ATO to prevent directly adding kalk powder to your tank.

thanks for the in depth response.

so 1/2 teaspoon is the max? is BRS lying?

1. Depending on your demand for calcium & alkalinity, add up to 2 teaspoons of BRS Pharma Kalkwasser to the reservoir.
   • Low Demand - 1/2 tsp per gallon of top off water.
   • Medium Demand - 1 tsp per gallon of top off water.
   • High Demand - 1 1/2 tsp per gallon of top off water.

my understanding was basically, start with 1/2 tsp and go from there. at 2 tsp per gallon, adding more won't do anything, so that's when people that supplement via kalk have to start dosing? but you're saying the max is 1/2 tsp?

also, i have my pump about 3-4" (intake towards the surface) above the bottom of my ATO reservoir. but you're thinking it's sucking in the undissolved stuff still?

so, you'd recommend taking a bucket of RODI and adding the kalk in there, then adding it to my ATO reservoir, but make sure to not add the undissolved stuff at the bottom?

 

[Justfebreezeit]

thanks for the in depth response.

so 1/2 teaspoon is the max? is BRS lying?



my understanding was basically, start with 1/2 tsp and go from there. at 2 tsp per gallon, adding more won't do anything, so that's when people that supplement via kalk have to start dosing? but you're saying the max is 1/2 tsp?

also, i have my pump about 3-4" (intake towards the surface) above the bottom of my ATO reservoir. but you're thinking it's sucking in the undissolved stuff still?

so, you'd recommend taking a bucket of RODI and adding the kalk in there, then adding it to my ATO reservoir, but make sure to not add the undissolved stuff at the bottom?

Honestly none of that was my experience with using kalk in the ato for over a year. I got up to 1 1/2 tsps per gallon and never had any substantial undissolved kalk on the bottom of my container. I held my pump off the bottom of the container 2 inches and mixed the kalk in the container itself.

The simple answer is you probably started with to much, even the BRS recommended 1/2 tsp per gallon starting amount is high IMO.

 

[mattzang]

Honestly none of that was my experience with using kalk in the ato for over a year. I got up to 1 1/2 tsps per gallon and never had any substantial undissolved kalk on the bottom of my container. I held my pump off the bottom of the container 2 inches and mixed the kalk in the container itself.

The simple answer is you probably started with to much, even the BRS recommended 1/2 tsp per gallon starting amount is high IMO.

hmm i see, well i think i'll try to clean it out tomorrow and do way less like 1 tsp per 5 gallons. and just gotta test alk daily i guess. and yeah my container is cloudy water, but there isn't a whole lot of stuff on the bottom really. but i still have the pump suspended anyway

i have a lot of corals in my tank, but probably most are lps/shrooms. i'm probably at like 10 sps frags, but given my fluctuating parameters they're probably not too happy and eating up much alkalinity lol

did you stop doing kalk at all or did you get a reactor? i intend to eventually get either the icecap or avast marine one, but i just wanted to do kalk and not spend a couple hundred more just to do so.

 

[Justfebreezeit]

hmm i see, well i think i'll try to clean it out tomorrow and do way less like 1 tsp per 5 gallons. and just gotta test alk daily i guess. and yeah my container is cloudy water, but there isn't a whole lot of stuff on the bottom really. but i still have the pump suspended anyway

i have a lot of corals in my tank, but probably most are lps/shrooms. i'm probably at like 10 sps frags, but given my fluctuating parameters they're probably not too happy and eating up much alkalinity lol

did you stop doing kalk at all or did you get a reactor? i intend to eventually get either the icecap or avast marine one, but i just wanted to do kalk and not spend a couple hundred more just to do so.

I upgraded tanks at the begging of the year so not much happening on my new one. But I eventually switched to a doser and have that hooked up now. I'm only dosing 1ml a day at this point though.

I did love kalk though, the corals seemed to do better with it than 2 part dosing (probably completely BS but who knows). I do want to get a calcium reactor in the future as well.

 

[mattzang]

I upgraded tanks at the begging of the year so not much happening on my new one. But I eventually switched to a doser and have that hooked up now. I'm only dosing 1ml a day at this point though.

I did love kalk though, the corals seemed to do better with it than 2 part dosing (probably completely crap but who knows). I do want to get a calcium reactor in the future as well.

did u run into pH issues? or did u not really worry about it?

i do notice a lot of people, back east especially, have tanks in their basement and stuff. but i'm in socal and my tank is right next to my front door, which is leave open for many hours a day, along with a lot of other doors. so i was kind of surprised my tank never had high pH naturally, but perhaps i just caught it recently on some bad days and my pH is naturally quite high? idk what the upper range of pH is, seems most want it at 8.4 at most, and i don't really aim to flirt with the absolute top range of anything

 

[sghera64]

I upgraded tanks at the begging of the year so not much happening on my new one. But I eventually switched to a doser and have that hooked up now. I'm only dosing 1ml a day at this point though.

I did love kalk though, the corals seemed to do better with it than 2 part dosing (probably completely crap but who knows). I do want to get a calcium reactor in the future as well.

I switched over from adding Kalk directly to my ATO to adding my ATO through a DIY calcium reactor: WAY more fun and simple. I simply fabricated a reactor out of 4" diameter clear PVC and a laboratory stir plate.

In my experience, adding undissolved Ca(OH)2 to the display tank, caused my alkalinity and calcium to drop. If I recall, my magnesium dropped too. I corrected this by adding a foam pad near the top of the reactor, stirring only for 2 minutes per hour (using a wall timer) and only allowing the ATO to flow through the reactor about 50 minutes after stirring (using a wall timer). That pretty much ensured any Ca(OH)2 or CaCO3 particulates in the reactor stayed near the bottom and only particulate free saturated kalkwasser flowed out of the top into my DT's overflow plumbing.

What I believe happens when Ca(OH)2 or CaCO3 particulates get into the system, they locally raise the pH around that particulate severely. This causes Mg, and Ca salts of carbonate to precipitate out (on to your pumps, heaters, plumbing, live rock, etc.).