what is the most used dKH level?

[wonderphil-reef]

Hi

So since starting my tank, which is now LPS and fish, I had believed that my Alkalinity should be in a range of 8-12 dKH. This was based on a couple of different sources.

Now over the weekend, I have been to a fish/coral shop and they told me I should be aiming for a range of 6.9-7.5 dKH and that's what they run all their setups on, which was a lot.

So my question is, what the? what should I be running at?

 

[t5Nitro]

I like to run mine at 7

 

[Randy Holmes-Farley]

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 are many different attributes of the aquarium...

www.reef2reef.com

I bolded the alk value recommendation below:

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 “buffersâ€. Most often, sodium carbonate is preferred, however, since most tanks can be helped by a pH boost.

 

[homer1475]

I personally have had less issues with SPS running around 6.8 to 7.5.

I would think the general consensus would be 8 to 8.5 though.

 

[wonderphil-reef]

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 are many different attributes of the aquarium...

www.reef2reef.com

I bolded the alk value recommendation below:

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 “buffersâ€. Most often, sodium carbonate is preferred, however, since most tanks can be helped by a pH boost.

That is brilliant, thanks very much @Randy Holmes-Farley

 

[DaJMasta]

As mentioned, lower dKH values can sometimes have issues with very low nutrient levels, so you have somewhat more flexibility so long as they're not trying to keep their nitrates and phosphates really low. There are people who insist on the lower levels (like what your LFS recommends) because it's similar to natural seawater, but then there are also studies showing that higher levels can yield faster growth and there's certainly appeal in that. There's also the fact that if you miss your dosing for whatever reason, a drop will not be ideal in either case, but a drop from an elevated level may be less risky to coral health than a drop when centered around a lower value, so there could be a benefit in terms of fault tolerance from a slightly elevated level.

All that said, it will be pretty dependent on the salt mix you use, unless you want to customize and buffer up levels in your chosen mix to change the baseline, and people have had huge success at any of these "acceptable" dKH levels of alkalinity. Pick one, get your tank there, and maintain it.

 

[blaxsun]

I like 8.25-8.5 dKH myself.

 

[Koh23]

8-ish is good middle, maintaing higher levels can be tricky, too much dosing....

8 is easy to maintain stable, maybe its not ideal, but serves the purpose

 

[Rmckoy]

I run mine at 7.5 dkh

 

[damsels are not mean]

I would think simply due to the popularity of IO salt most tanks are around 11. The answer should just be whatever you can maintain though. The most important thing is that it is stable, not the number (unless it's outside that range). It is really the only parameter besides I suppose ammonia that needs to be completely rock solid.

 

[gbroadbridge]

Hi

So since starting my tank, which is now LPS and fish, I had believed that my Alkalinity should be in a range of 8-12 dKH. This was based on a couple of different sources.

Now over the weekend, I have been to a fish/coral shop and they told me I should be aiming for a range of 6.9-7.5 dKH and that's what they run all their setups on, which was a lot.

So my question is, what the? what should I be running at?

My tanks run at 7.5 dKh - Mixed Reef.

 

[Uriken]

Randy,. Thanks for the information. As always I learned a few things as well as it confirmed some recent thinking. I just went through my 1st tank crash on a 20+ year old reef tank. I have always used Reef Crystals mainly cause of the fact that back in the day it was one of the better brands available and the cost was respectable. One thing that is apparent with Reef Crystals is the elevated levels. Mainly the ALK. 12 to 12.5 mixed out of the bucket. Depending on water change frequency and the use of ESV Bionic 2-part it can be a juggle trying to keep things at normal range and steady. I found scenarios with ALK at 12 / 12+ but the Calcium lingering around 360-380 being off balance after a few days. When it happens it can get hard to even out if not careful. Since I brushed my self off and decided to start up another tank (smaller this time) I'm considering going with the Red Sea Blue Bucket as the levels are more realistic to the normal range at mixing. The Black Bucket I tried a few years back but it was similar to the Reef Crystals containing elevated levels right out of the bucket. I think Id rather have lower levels and maintain evenly with the 2-part keeping it steady.

 

[bnord]

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 are many different attributes of the aquarium...

www.reef2reef.com

I bolded the alk value recommendation below:

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 “buffersâ€. Most often, sodium carbonate is preferred, however, since most tanks can be helped by a pH boost.

superb explanation for the beginner and intermediate alike - thank you

 

[LeftyReefer]

Mine is currently at 7.0.

Just put a doser online and plan to bring it back up to 7.5 slowly.
no more dosing by hand. hopefully the doser, dosing multiple times per day now can keep my ALK more steady.

 

[Jwise]

I like to run a tank with an alk of 10 to 10.5 it has been a good buffer to keep it there so i know i wont be easy to slip and let it go to low based on sps and lps growth and would have enough time to react if i do notice an uptake in alk so it doesnt drop below crucial levels

 

[bnord]

And to the OP, have two sister tanks, different dimensions, mostly same equipment and same RODI and water mixes, WC schedules - difference is one employs All for Reef and the other Kalkwasser and a 2 part

both tested 2-3 times a week for dkh, and 1-2X per month for Ca Mg and others

AfR runs a consistent 8.4-8.8 and the 2 part Kalk id 9.9 -10.4. when I test pH, (not that often) it runs 0.2 higher in the 2 part tank. 8.1 to 8.3 (have outdoor air running to the skimmers).

Both grow SPS and LPS just about the same, so to the point the 7.0 to 12. is a huge range and can seem contradictive. - But I like to be higher than lower.

by the way, in one of my 2 BIG self imposed disasters, I had a ATO with Kalk overflow (never again) and ran it up to 15 - kilt a bunch of SPS and as Randy says, turned big chunks of the sand to concrete -

 

[BWV]

What is the recommended product for a small tank? (fluval evo.. ~10.5 gal water)

I use baked baking soda (soda ash) constantly dose and have a hard time keeping it above 7.7 DKH

 

[Reeferbadness]

I run both of my mixed reef tanks (180 and 200 g) at about 9.0. This gives me a buffer if the dosiing system fails and i don't test for a few days.

 

[Jwise]

What is the recommended product for a small tank? (fluval evo.. ~10.5 gal water)

I use baked baking soda (soda ash) constantly dose and have a hard time keeping it above 7.7 DKH

I personally use red sea products for all my minerals, trace elements, and aminos and have found that they work really well just be careful as they are all super concentrated and you should take care dosing and start doing about half than recomended on the bottle and see how your tank reacts and test every week to see what it gets raised to. It would be best to split that amount you dose into two seperate days. An example is when i do my tank I dose a half of what i need to dose on tuesday and then the other half on friday. If you have an automatic doser then just set it to what i said to make sure its not to much for you tank and lower or raise the dose based on what your test results bring back every week until you have it dialed in. Then i would test your elements every two weeks if you have lps and softies and i would test every week if you have sps to make sure that your alk dosent change rapidly with thier growth.

 

[Jwise]

I personally use red sea products for all my minerals, trace elements, and aminos and have found that they work really well just be careful as they are all super concentrated and you should take care dosing and start doing about half than recomended on the bottle and see how your tank reacts and test every week to see what it gets raised to. It would be best to split that amount you dose into two seperate days. An example is when i do my tank I dose a half of what i need to dose on tuesday and then the other half on friday. If you have an automatic doser then just set it to what i said to make sure its not to much for you tank and lower or raise the dose based on what your test results bring back every week until you have it dialed in. Then i would test your elements every two weeks if you have lps and softies and i would test every week if you have sps to make sure that your alk dosent change rapidly with thier growth.

Water changes may help but i dont recommend constantly doing them other than maybe every other week to a month and wouldnt do more than a 25% water change.