KH and CA testing

[jswo]

A little confused on my CA and KH testing. Right now using AQUAVITRO brand Calcification to raise my CA which is 400 right now and then using same brand EIGHT FOUR for the alk but don't know if that's the correct two to use together. KH is at 11% but PH is at 8.2 most of the day, it goes from 8.1 to 8.3. Also am using a Apex controller for PH, temp, salinity. My temp goes from 77 to 82, have a woodstove and its hard to keep temp stable in house. Also testing in early evening at same time. My test for CA and KH is done with api tests, guess my ? is what am I looking for in KH and CA tests and is AQUAVITRO chemicals ok. Let me know if theres anything else I can post to help.

 

[Randy Holmes-Farley]

Aquavitro chemicals are fine. A two part might be easier, but use what you have for now.

The pH is fine and the eight four should only be added to boost alkalinity, not pH. Since the alkalinity is on the high end now, don't dose more if it until the alkalinity declines

Calcium is also fine, but boosting it another 20 ppm would be an ok plan.

 

[Randy Holmes-Farley]

The temp swing is ok as well.

 

[jswo]

Was told the 8 4 would raise the pH to 8.4 so that's what I was going for. Still have a lot to learn, you said I should get a 2 part system and it is or if it's not what would be a 2 part?

 

[Randy Holmes-Farley]

The 8.4 comment is totally wrong, despite the manufacturer claiming it.

All it really means is that when first added to seawater, it tends to drive the pH in the direction of 8.4 from wherever it is at the time.

But pH is controlled only by the CO2 level in the water and the alkalinity.

A two part system means two different products designed to work together. One bottle has alkalinity, the other has calcium (and usually magnesium). You dose the two parts equally.

These have more:


The “How To” Guide to Reef Aquarium Chemistry for Beginners Part 1: The Salt Water Itself by Randy Holmes-Farley - Reefkeeping.com

The “How To” Guide to Reef Aquarium Chemistry for Beginners Part 2: What Chemicals Must be Supplemented by Randy Holmes-Farley - Reefkeeping.com

The “How To” Guide to Reef Aquarium Chemistry for Beginners Part 3: pH by Randy Holmes-Farley - Reefkeeping.com

The “How To” Guide to Reef Aquarium Chemistry for Beginners Part 4: What Chemicals May Detrimentally Accumulate by Randy Holmes-Farley - Reefkeeping.com

 

[jswo]

So what does the 8 4 do then? What would you recommend for the alk then?

 

[Randy Holmes-Farley]

It is a marketing gimmick.

It is an alkalinity supplement, like most others, which contain carbonate, bicarbonate, or both.

It happens to have (or at least should have) the same ratio of bicarbonate to carbonate as exists in seawater at pH 8.4, which is more bicarbonate than carbonate.

If you dose just carbonate, you will get a bigger pH raising effect than any buffer which also contains bicarbonate. It is about 0.3 pH units for each 1.4 dKH of alkalinity added, but the effect is temporary, until teh aquarium re-equilibrates with the CO2 in the room.

If you dose just bicarbonate, you will get a slight pH lowering effect. It is about 0.06 pH units for each 1.4 dKH of alkalinity added, but again, the effect is temporary, until the aquarium re-equilibrates with the CO2 in the room.

Both supplements will attain the same tank pH after sufficient time for re-equilibration.

I discuss my recommendations here (and much more extensively in other articles):

https://www.reef2reef.com/forums/re...-coral-reef-aquarium-randy-holmes-farley.html

from it:


Critical Parameters


Calcium


Many corals use calcium to form their skeletons, which are composed primarily of calcium carbonate. The corals get most of the calcium for this process from the surrounding water. Consequently, calcium often becomes depleted in aquaria housing rapidly growing corals, calcareous red algae (coralline algae), Tridacnids (clams) and Halimeda (a macroalgae containing calcium carbonate). As the calcium level drops below 360 ppm, it becomes progressively more difficult for these organisms to collect enough calcium, thus stunting their growth.


Maintaining the calcium level is one of the most important aspects of coral reef aquarium husbandry. Most reef aquarists try to maintain approximately natural levels of calcium in their aquaria (~420 ppm). It does not appear that boosting the calcium concentration above natural levels enhances calcification (i.e., skeletal growth) in most corals.


For these reasons, I suggest that aquarists maintain a calcium level between about 380 and 450 ppm, although higher is generally not a problem until it gets so high that calcium carbonate precipitation becomes problematic. Aquarists with a very light demand may be able to maintain calcium with water changes, especially since some salt mixes have excessive calcium in them. But most established aquaria with growing hard corals and coralline algae will require some calcium supplementation, and in some cases, it might be needed every day.


I usually suggest using a balanced calcium and alkalinity additive system for routine maintenance. The most popular of these balanced methods include limewater (kalkwasser), calcium carbonate/carbon dioxide reactors, and the two-part or three-part additive systems for calcium and alkalinity. If calcium is depleted and needs to be raised significantly, however, such balanced methods are not a good choice since they will raise alkalinity too much. In that case, adding calcium chloride is a good method for raising calcium in a one-time correction.


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.

 

[srgibbs67]

Wow, great info. Tks.

 

[Randy Holmes-Farley]

You're welcome.

Happy Reefing.

 

[DFW]

It is a marketing gimmick.

It is an alkalinity supplement, like most others, which contain carbonate, bicarbonate, or both.

It happens to have (or at least should have) the same ratio of bicarbonate to carbonate as exists in seawater at pH 8.4, which is more bicarbonate than carbonate.

If you dose just carbonate, you will get a bigger pH raising effect than any buffer which also contains bicarbonate. It is about 0.3 pH units for each 1.4 dKH of alkalinity added, but the effect is temporary, until teh aquarium re-equilibrates with the CO2 in the room.

If you dose just bicarbonate, you will get a slight pH lowering effect. It is about 0.06 pH units for each 1.4 dKH of alkalinity added, but again, the effect is temporary, until the aquarium re-equilibrates with the CO2 in the room.

Both supplements will attain the same tank pH after sufficient time for re-equilibration.

I discuss my recommendations here (and much more extensively in other articles):

https://www.reef2reef.com/forums/re...-coral-reef-aquarium-randy-holmes-farley.html

from it:


Critical Parameters


Calcium


Many corals use calcium to form their skeletons, which are composed primarily of calcium carbonate. The corals get most of the calcium for this process from the surrounding water. Consequently, calcium often becomes depleted in aquaria housing rapidly growing corals, calcareous red algae (coralline algae), Tridacnids (clams) and Halimeda (a macroalgae containing calcium carbonate). As the calcium level drops below 360 ppm, it becomes progressively more difficult for these organisms to collect enough calcium, thus stunting their growth.


Maintaining the calcium level is one of the most important aspects of coral reef aquarium husbandry. Most reef aquarists try to maintain approximately natural levels of calcium in their aquaria (~420 ppm). It does not appear that boosting the calcium concentration above natural levels enhances calcification (i.e., skeletal growth) in most corals.


For these reasons, I suggest that aquarists maintain a calcium level between about 380 and 450 ppm, although higher is generally not a problem until it gets so high that calcium carbonate precipitation becomes problematic. Aquarists with a very light demand may be able to maintain calcium with water changes, especially since some salt mixes have excessive calcium in them. But most established aquaria with growing hard corals and coralline algae will require some calcium supplementation, and in some cases, it might be needed every day.


I usually suggest using a balanced calcium and alkalinity additive system for routine maintenance. The most popular of these balanced methods include limewater (kalkwasser), calcium carbonate/carbon dioxide reactors, and the two-part or three-part additive systems for calcium and alkalinity. If calcium is depleted and needs to be raised significantly, however, such balanced methods are not a good choice since they will raise alkalinity too much. In that case, adding calcium chloride is a good method for raising calcium in a one-time correction.


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.

Randy, thanks for all your help!

I had an alkalinity drop today since yesterday of about 1.1 dKH, which seems odd, since it has been consistent for a while. So I brought out my Seachem Total alk test kit - I always use API KH test kit - and whereas the API showed about 9.2 dKH, the Seachem showed 10.5 dKH. I have been keeping the alk at about 10.3 using the API test kits for several years. I test in the evening before I mix up my lime water for over night dripping. I am thinking that there should not be this much variation between the test kits. I don't have anything forming on heaters, or pumps, so don't think that I have been keeping alk too high. Magnesium is at 1625. Calcium 480. I am letting these drop when I can. I have been supplementing daily with a slurry of washing soda lately because the almost 2 gallons daily of saturated lime water is not quite keeping up with demand.

Any observations/suggestions would be very much appreciated!

 

[Rob Top1]

Hey DFW, did API come out with a new version of their kit? Only one I have ever seen gives results in whole numbers equal to drops used.

 

[Randy Holmes-Farley]

I am thinking that there should not be this much variation between the test kits.

An all too frequent complaint with many types of kits.

One way an alk kit can start of accurate and become less so is if the liquid you add has evaporated.

There may also be inherent differences between kits if they use different indicators dyes and so "call" the endpoint of the test at different pH values.

And, of course, they can be made less than perfectly. The acid titrant can be of variable concentration and the volume measurements may be incorrect somehow.

Assuming you have accurate ways to measure volume, my DIY alk test will have the accuracy to say which (if either) is correct. The directions will publish around Jan 1.

If the primary concern is changes to alkalinity, using just one of the kits may be more useful if one typically reads higher than the other.

 

[DFW]

Hey DFW, did API come out with a new version of their kit? Only one I have ever seen gives results in whole numbers equal to drops used.

It is still just whole numbers. If you add 9 drops, and the liquid has just the faintest blue color, I call it 9.1. If after 9 drops it is not quite as dark as it was after 8 drops, it might be 9.8, or 9.9. If after 9 drops it appears to be about half as dark as after 8 drops, then it might be close to 9.5. I thought that everybody did it this way, but come to think of it, it is not in the instructions.

 

[DFW]

An all too frequent complaint with many types of kits.

One way an alk kit can start of accurate and become less so is if the liquid you add has evaporated.

There may also be inherent differences between kits if they use different indicators dyes and so "call" the endpoint of the test at different pH values.

And, of course, they can be made less than perfectly. The acid titrant can be of variable concentration and the volume measurements may be incorrect somehow.

Assuming you have accurate ways to measure volume, my DIY alk test will have the accuracy to say which (if either) is correct. The directions will publish around Jan 1.

If the primary concern is changes to alkalinity, using just one of the kits may be more useful if one typically reads higher than the other.

Thank you, sir! Yes, consistency is primary to me! I will look forward to your coming article!

 

[Randy Holmes-Farley]

You're welcome.

Happy Reefing.

 

[bkelley02]

An all too frequent complaint with many types of kits.

One way an alk kit can start of accurate and become less so is if the liquid you add has evaporated.

There may also be inherent differences between kits if they use different indicators dyes and so "call" the endpoint of the test at different pH values.

And, of course, they can be made less than perfectly. The acid titrant can be of variable concentration and the volume measurements may be incorrect somehow.

Assuming you have accurate ways to measure volume, my DIY alk test will have the accuracy to say which (if either) is correct. The directions will publish around Jan 1.

If the primary concern is changes to alkalinity, using just one of the kits may be more useful if one typically reads higher than the other.

Randy,

Will you still be doing this? I have two test kits from Red Sea (one pro, other not) and one reads at 8 while the other is around 14-14.3 range. Needless to say, I have little confidence in either right now.

Thanks,

Brian

 

[Randy Holmes-Farley]

Randy,

Will you still be doing this? I have two test kits from Red Sea (one pro, other not) and one reads at 8 while the other is around 14-14.3 range. Needless to say, I have little confidence in either right now.

Thanks,

Brian

The DIY alk test should post tomorrow as part of R2R's new magazine.