What do the numbers mean in relation to actual usage?

[uhgster1]

I am finally at the point where I must dose to keep my parameters stable. Can anyone explain in layman’s terms what the actual numbers mean? If for example alkalinity comes in at 6.2 dkh with kalk providing the alkalinity and calcium, does that mean that the corals have what they need and I am just bringing the levels up for availability, or are the numbers supposed to be higher (8-9 dkh) in order for the coral to be able to use the elements? I ask because if it is just for availability then it makes sense to dose slowly to bring the numbers up, but if is because they need a certain number just to metabolize then dosing to the correct numbers quickly makes sense. I know that adding quickly is damaging but I just want to understand what we are actually doing when we dose in simple terms. Thanks !

 

[Lasse]

6.2 in dKH works but I prefer around 7. Other prefer higher. If you dose in a way that you have your decided value around your decided level - you are fine. If it rise - you dose too much according to demands - if it decline - you dose too little for your demand. Note - the demand can vary especially when corals grow

Sincerelöy Lasse

 

[ReefBeta]

They don't need much of certain number. Mostly just availability. The number means concentration. When it gets relatively low, like less than 6, it would become more difficult for coral to take it out from water column.

So it's still a good idea to raise it to have safe buffer zone. Raise it slowly is better for most cases. But I will probably raise it back to 7 in two days then slow down to like 0.2 a day.

 

[PatW]

Randy has a sticky giving the values of the parameters in “normal” sea water (NSW). On some thing home aquaria run far higher than NSW like nitrates and phosphates. In some, people run things a bit high like Mg, Ca, and ALK.

 

[mdb_talon]

All else being equal stony coral will grow faster at higher alkalinity....to a point. It will grow skeleton faster at 9 than it will at 6. I would say bare minimum you want is 7. Obviously getting alk too high has other risks and issues so while you can run at 12 in some systems there is no margin for error. I think most people run at 8-11 range

 

[Bacon505]

All else being equal stony coral will grow faster at higher alkalinity....to a point. It will grow skeleton faster at 9 than it will at 6. I would say bare minimum you want is 7. Obviously getting alk too high has other risks and issues so while you can run at 12 in some systems there is no margin for error. I think most people run at 8-11 range

Not necessary true, it more stability base than actual numbers. My alk run between 5.8-6.5 for the most part an i have no issue growing sps. There’s an ideal range that give you more flexibility but the importance is keeping it stable.

 

[mdb_talon]

Not necessary true, it more stability base than actual numbers. My alk run between 5.8-6.5 for the most part an i have no issue growing sps. There’s an ideal range that give you more flexibility but the importance is keeping it stable.

Stability is important yes...thus why i said "all else being equal". There is plenty of evidence stony growth is faster at a dkh of 8 than at 6 though for example...again all else being equal. If you start getting to 10+ then need to start worrying about nutrient levels more, but on the lower side of the range a higher dkh will be faster growth....all else being equal.

Also to clarify i did not say you cant grow sps at 7(or even 6)..just that there is a relationship between the alk levels and speed of growth. I will say once you get to the levels you are speaking of(5.8-6.5) stability may be easier because the coral is growing much slower and utilizing less.

 

[Bacon505]

This is my 9 months growth at very low alk and cal. So i can’t concur that “coral grow much slower” at lower alk.

 

[mdb_talon]

Lol fortunately we dont have to agree. However i will stick with science about a relationship between faster growth and higher alkalinity(again all else being equal and within reason).

 

[Lasse]

However i will stick with science about a relationship between faster growth and higher alkalinity

Have you anything - scientific articles as an example - to back this up that you at - let us say 8 dKH and 440 mg/L Ca have faster growth compared with 6 dKH and 440 mg/L Ca. It is not either my experiences

Sincerely Lasse

 

[Randy Holmes-Farley]

I am finally at the point where I must dose to keep my parameters stable. Can anyone explain in layman’s terms what the actual numbers mean? If for example alkalinity comes in at 6.2 dkh with kalk providing the alkalinity and calcium, does that mean that the corals have what they need and I am just bringing the levels up for availability, or are the numbers supposed to be higher (8-9 dkh) in order for the coral to be able to use the elements? I ask because if it is just for availability then it makes sense to dose slowly to bring the numbers up, but if is because they need a certain number just to metabolize then dosing to the correct numbers quickly makes sense. I know that adding quickly is damaging but I just want to understand what we are actually doing when we dose in simple terms. Thanks !

from one of my articles:

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.

 

[mdb_talon]

Have you anything - scientific articles as an example - to back this up that you at - let us say 8 dKH and 440 mg/L Ca have faster growth compared with 6 dKH and 440 mg/L Ca. It is not either my experiences

Sincerely Lasse

There are several studies a quick google search can lead you to. One of them may lead you to the the Randy's article that he just quoted part of. I believe that was probably the first one i read years ago that made me look further into it. Actual studies have been done and from everything i have seen there is good evidence that many corals grow faster in higher alkalinity(though not all), but those that dont dont see a decrease in growth at higher alk.

There is also a good BRS video if i remember correctly (though much of their focus is on how alk impacts PH -both increasing and minimizing swings)

 

[Lasse]

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.

See my bold. As I see it - Randy is unsure of this because he use the word may in this article. And I do not really know - I only asked if you can point me to some studies that show that this is really happens. Or @Randy Holmes-Farley - you maybe can point me in that direction. My experiences in some way tell a different story

According to BRS - I´m not rather sure that the alkalinity when it comes up to our levels and in our aquarium have as much impact on pH as we normally think. IME - the CO2 level in the air around the aquarium and the internal bacterial process plus the amount of organism that use photosynthesis are those factors that impact the average pH and also mostly the swing.

Sincerely Lasse