Switching from AFR to kalkwasser

[jimsreef]

I have a 3 year old mixed reef medium stocked 90 gallon. I have been dosing AFR (50) ml a day. Keep me between 7 and 8 dkh. My pH is low due to CO2 in winter months. I have tried outside air to the skimmer and scrubbers but it never worked for me. So I'm thinking of dosing kalk and adding trace elements hoping to raise my pH. My pH is 7.6 to 7.9 currently. Summer time it runs 8 to 8.2. my question is how much kalkwasser would I need to dose.

 

[Randy Holmes-Farley]

If the pH rises, demand may rise, but 50 mL of AFR is equivalent to 2.6 Liters of saturated kalkwasser.

 

[jimsreef]

That would be almost as much as my top off water.

 

[Randy Holmes-Farley]

That would be almost as much as my top off water.

Exactly. That is the main limitation of kalkwasser.

 

[jimsreef]

2.6 liters would be 2600 ml. Over a 12 hr period at night that would be dosing about 217 ml per hr. That sounds right?

 

[jimsreef]

Randy what do you keep your alkalinity at?

 

[Randy Holmes-Farley]

2.6 liters would be 2600 ml. Over a 12 hr period at night that would be dosing about 217 ml per hr. That sounds right?

Yes. That high amount if why some folks put kalkwasser into their ATO.

 

[jimsreef]

My ATO is gravity fed. It would put it in all day instead of just at night.

 

[Randy Holmes-Farley]

Randy what do you keep your alkalinity at?

My tank is not currently up. I recommend 7-11 dKH, with higher alk leading to higher fast coral growth in many cases.

Optimal Parameters for a Coral Reef Aquarium: By Randy Holmes-Farley

[note: edited on 5/29/2022 to update the nitrate and phosphate sections with higher recommended levels.] One of the main roles of an aquarist with a coral reef aquarium is to ensure that the conditions are right for their tank inhabitants. There...

www.reef2reef.com

Alkalinity

Like calcium, many corals also use "alkalinity" to form their skeletons, which are composed primarily of calcium carbonate. It is generally believed that corals take up bicarbonate, convert it into carbonate, and then use that carbonate to form calcium carbonate skeletons. That conversion process is shown as:

HCO3- → CO3-- + H+

Bicarbonate → Carbonate + proton (which is released from the coral)

To ensure that corals have an adequate supply of bicarbonate for calcification, aquarists could just measure bicarbonate directly. Designing a test kit for bicarbonate, however, is somewhat more complicated than for alkalinity. Consequently, the use of alkalinity as a surrogate measure for bicarbonate is deeply entrenched in the reef aquarium hobby.

So, what is alkalinity? Alkalinity in a marine aquarium is simply a measure of the amount of acid (H+) required to reduce the pH to about 4.5, where all bicarbonate is converted into carbonic acid as follows:

HCO3- + H+ → H2CO3

The amount of acid needed is equal to the amount of bicarbonate present, so when performing an alkalinity titration with a test kit, you are counting the number of bicarbonate ions present. It is not, however, quite that simple since some other ions also take up acid during the titration. Both borate and carbonate also contribute to the measurement of alkalinity, but the bicarbonate dominates these other ions since they are generally lower in concentration than bicarbonate. So knowing the total alkalinity is akin to, but not exactly the same as, knowing how much bicarbonate is available to corals. In any case, total alkalinity is the standard that aquarists use for this purpose.

Unlike the calcium concentration, it is widely believed that certain organisms calcify more quickly at alkalinity levels higher than those in normal seawater. This result has also been demonstrated in the scientific literature, which has shown that adding bicarbonate to seawater increases the rate of calcification in some corals. Uptake of bicarbonate can consequently become rate limiting in many corals. This may be partly due to the fact that the external bicarbonate concentration is not large to begin with (relative to, for example, the calcium concentration, which is effectively about 5 times higher).

For these reasons, alkalinity maintenance is a critical aspect of coral reef aquarium husbandry. In the absence of supplementation, alkalinity will rapidly drop as corals use up much of what is present in seawater. Water changes are not usually sufficient to maintain alkalinity unless there is very little calcification taking place. Most reef aquarists try to maintain alkalinity at levels at or slightly above those of normal seawater, although exactly what levels different aquarists target depends a bit on the goals of their aquaria.

Interestingly, because some corals may calcify faster at higher alkalinity levels, and because the abiotic (nonbiological) precipitation of calcium carbonate on heaters and pumps also rises as alkalinity rises, the demand for alkalinity (and calcium) rises as the alkalinity rises. So an aquarist generally must dose more calcium and alkalinity EVERY DAY to maintain a higher alkalinity (say, 11 dKH) than to maintain 7 dKH. It is not just a one-time boost that is needed to make up that difference. In fact, calcification gets so slow as the alkalinity drops below 6 dKH that reef aquaria rarely get much below that point, even with no dosing: natural calcification has nearly stopped at that level.

In general, I suggest that aquarists maintain alkalinity between about 7-11 dKH (2.5 and 4 meq/L; 125-200 ppm CaCO3 equivalents). Many aquarists growing SPS corals and using Ultra Low Nutrient Systems (ULNS) have found that the corals suffer from "burnt tips" if the alkalinity is too high or changes too much. It is not at all clear why this is the case, but such aquaria are better served by alkalinity in the 7-8 dKH range.
As mentioned above, alkalinity levels above those in natural seawater increase the abiotic precipitation of calcium carbonate on warm objects such as heaters and pump impellers, or sometimes even in sand beds. This precipitation not only wastes calcium and alkalinity that aquarists are carefully adding, but it also increases equipment maintenance requirements and can "damage" a sand bed, hardening it into a chunk of limestone. When elevated alkalinity is driving this precipitation, it can also depress the calcium level. An excessively high alkalinity level can therefore create undesirable consequences.

I suggest that aquarists use a balanced calcium and alkalinity additive system of some sort for routine maintenance. The most popular of these balanced methods include limewater (kalkwasser), calcium carbonate/carbon dioxide reactors, and the two-part/three part additive systems.

For rapid alkalinity corrections, aquarists can simply use baking soda (sodium bicarbonate) or washing soda (sodium carbonate; baked baking soda) to good effect. The latter raises pH as well as alkalinity while the former has a very small pH lowering effect. Mixtures can also be used, and are what many hobby chemical supply companies sell as buffers. Most often, sodium carbonate is preferred, however, since most tanks can be helped by a pH boost.

 

[Randy Holmes-Farley]

My ATO is gravity fed. It would put it in all day instead of just at night.

That's what I did (24/7 dosing, but by pump), but a dosing pump at night is a fine plan.

 

[Ruben's Reef]

I have a 3 year old mixed reef medium stocked 90 gallon. I have been dosing AFR (50) ml a day. Keep me between 7 and 8 dkh. My pH is low due to CO2 in winter months. I have tried outside air to the skimmer and scrubbers but it never worked for me. So I'm thinking of dosing kalk and adding trace elements hoping to raise my pH. My pH is 7.6 to 7.9 currently. Summer time it runs 8 to 8.2. my question is how much kalkwasser would I need to dose.

Im currently dosing AFR 60ml per day, using the Reef moonshiners method and my alk is seating at 7.8 while my PH goes from 7.9-8.2 specially duting the day. I use to dose kalkwaisser at night to raise the PH but I dont see any difference on PH so I stop dosing kalkwaisser. What I like of AFR is how keep most of the elements well balanced exept of some that deplete just a little. After a Oceamo MS test the corrections I have to make are minimum. Overall corals are growing well, some montiporas overgrowing like weed. I also run a refiugum with chaeto but I stop chasing PH and let the tank run on its own.

 

[Peair]

I have a 3 year old mixed reef medium stocked 90 gallon. I have been dosing AFR (50) ml a day. Keep me between 7 and 8 dkh. My pH is low due to CO2 in winter months. I have tried outside air to the skimmer and scrubbers but it never worked for me. So I'm thinking of dosing kalk and adding trace elements hoping to raise my pH. My pH is 7.6 to 7.9 currently. Summer time it runs 8 to 8.2. my question is how much kalkwasser would I need to dose.

I use Continuum Aquatics Reef Basis Kalkwasser, you want to Dissolve 6 grams, about 2 teaspoons of Kalk in 1 gallon of purified water to make a saturated solution, than I dose 6ML a day in 53 gal. tank, it helps keep my PH steady at 8.28.

 

[Randy Holmes-Farley]

I dose 6ML a day in 53 gal. tank, it helps keep my PH steady at 8.28.

Do you mean that exactly as written? If so, it is doing almost nothing. It is not helping pH in a way you can detect.

 

[exnisstech]

Im currently dosing AFR 60ml per day, using the Reef moonshiners method and my alk is seating at 7.8 while my PH goes from 7.9-8.2 specially duting the day. I use to dose kalkwaisser at night to raise the PH but I dont see any difference on PH so I stop dosing kalkwaisser. What I like of AFR is how keep most of the elements well balanced exept of some that deplete just a little. After a Oceamo MS test the corrections I have to make are minimum. Overall corals are growing well, some montiporas overgrowing like weed. I also run a refiugum with chaeto but I stop chasing PH and let the tank run on its own.

I had similar results as far as pH while using kalk. I was dosing 7200ml a day and never noticed any difference in pH between the tank getting kalk and two other tanks on AFR and 2part. When I tested all 3 tanks had the same results testing with a Hanna pH tester. That said I don't worry about pH, I just tested out of curiosity to see if there were any differences between the 3 tanks I have running.

 

[Peair]

Do you mean that exactly as written? If so, it is doing almost nothing. It is not helping pH in a way you can detect.

It works very good, I think it's Consistency why it works so good, look up: Continuum Aquatics Reef Basis Kalkwasser, you do not want to dose a lot. It helps maintain a very good PH. The best dose for a 53 gal tank is: dose 6ML a day in 53 gal. tank, it helps keep my PH steady at 8.28.

 

[Randy Holmes-Farley]

It works very good, I think it's Consistency why it works so good, look up: Continuum Aquatics Reef Basis Kalkwasser, you do not want to dose a lot. It helps maintain a very good PH. The best dose for a 53 gal tank is: dose 6ML a day in 53 gal. tank, it helps keep my PH steady at 8.28.

I'm sorry, you are mistaken. I know what kalkwasser is: calcium hydroxide dissolved in water.

Adding 6 ml to 53 gallons boosts alkalinity by less than 0.01 dKH, and will boost pH by far less than 0.01 pH unit.

Kalkwasser is generally added at a rate close to 1-2% of the total tank volume.

 

[Peair]

I'm sorry, you are mistaken. I know what kalkwasser is: calcium hydroxide dissolved in water.

Adding 6 ml to 53 gallons boosts alkalinity by less than 0.01 dKH, and will boost pH by far less than 0.01 pm unit.

Kalkwasser is generally added at a rate close to 1-2% of the total tank volume.

I have been using this Kalk a long time, I started using using it on a practice tank at 43ML a day and it would spike Calcium too high, I than divided it by 7 and came up with 6ml a day, and than very little Calcium increase, and than after I found a safe dose, I dose 6ml a day in my main 53 gal tank, I have experience using this, you don't, you have to be very careful with Kalk to find the right dose, and this Kalk is safe if you use the right dose, and it does maintain a very good PH if you use it right.

 

[rishma]

My ATO is gravity fed. It would put it in all day instead of just at night.

I am a long time kalkwasser user (and I use AFR too). One caution based on experience, the float valve for gravity feed ATO with Kalk will build up deposits and could potentially leak by. You need to be disciplined about keeping it clean or may run into a problem.

 

[rishma]

I have been using this Kalk a long time, I started using using it on a practice tank at 43ML a day and it would spike Calcium too high, I than divided it by 7 and came up with 6ml a day, and than very little Calcium increase, and than after I found a safe dose, I dose 6ml a day in my main 53 gal tank, I have experience using this, you don't, you have to be very careful with Kalk to find the right dose, and this Kalk is safe if you use the right dose, and it does maintain a very good PH if you use it right.

I suggest you look up who Randy is, perhaps read some is his many articles including those about Kalkwasser. I suspect you’ll learn some helpful things.

Perhaps what you are using is not just calcium hydroxide

 

[Peair]

I suggest you look up who Randy is, perhaps read some is his many articles including those about Kalkwasser. I suspect you’ll learn some helpful things.

I am just explaining what works for me and my tank, it took me a long time to get the Kalk I use right, you have to be very careful with Kalk, and I learn through trial and error.