Poll: Alkalinity - Daily Demand

BRS

What is your daily Alkalinity demand in dKH?

  • .1-.5

    Votes: 254 36.7%
  • .6-1.0

    Votes: 164 23.7%
  • 1.1-1.5

    Votes: 129 18.6%
  • 1.6-2.0

    Votes: 61 8.8%
  • 2.0-2.5

    Votes: 41 5.9%
  • 2.6-3.0

    Votes: 14 2.0%
  • >3.0

    Votes: 29 4.2%

  • Total voters
    692

dbl

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Yesterday we discussed stability. Many commented (and I agree) alkalinity is probably the most important of the parameters to maintain stability. (Yes salinity and temperature rank up there also).

We did a poll a while ago that asked what your average dKH measures in your systems. The vast majority of responses was in the range of 8.0-8.5 dKH. I thought it might be interesting to look at what your daily demand is in terms of dKH. Yes, this will vary from system to system and be determined by many factors. This poll is just to get a feel for the daily demands that we have to supplement for to maintain stability.
 

ksfulk

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I'm surprised at how many people voted 0-1 dKH per day. Maybe many of them are new tanks or keep lower alk/lower pH systems.

Ive always been surprised at how low my alk consumption is for how large my tank is (~120 gallons). After a year and a few dozen sps Im still only dosing about 30mL of ESV B-Ionic Daily. But I keep my alk lower than most (~6.7-7.0 dKH), so I suspect that is part of it.
 

PEP12

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I am dosing 70ml of Red Sea reef foundation B daily and my KH is in the region of 9.0 my system is a heavily mixed reef with fish and 540ltrs (118 G) I would like to know if this is where it should be or not ?
 

Randy Holmes-Farley

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I am dosing 70ml of Red Sea reef foundation B daily and my KH is in the region of 9.0 my system is a heavily mixed reef with fish and 540ltrs (118 G) I would like to know if this is where it should be or not ?

Are you asking about the alkalinity current/target value of 9 dKH (we'd need to know more about the tank and your goals to answer), or the amount of the additive you are using to get there?
 

PEP12

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Thanks for reply, as I stated I am dosing 70ml per day to keep it around 9dkh, if I reduce this amount my PH drops away and at present it is averaging 8.1 my other parameter averages are no3 5ppm, calcium 450ppm, po4 0.03
Mag 1410ppm, salinity 1.026, I wish the DKH to stay around 9, all the inhabitants within the tank are growing in size fine, I hope this answers your question as I am still learning all of this.
 

Randy Holmes-Farley

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Thanks for reply, as I stated I am dosing 70ml per day to keep it around 9dkh, if I reduce this amount my PH drops away and at present it is averaging 8.1 my other parameter averages are no3 5ppm, calcium 450ppm, po4 0.03
Mag 1410ppm, salinity 1.026, I wish the DKH to stay around 9, all the inhabitants within the tank are growing in size fine, I hope this answers your question as I am still learning all of this.

I wouldn't pick an optimal alkalinity target based on pH effects as a primary consideration.

That said, here's my discussion on alkalinity and why one might pick different values:

Optimal Parameters for a Coral Reef Aquarium: By Randy Holmes-Farley
https://www.reef2reef.com/forums/re...-coral-reef-aquarium-randy-holmes-farley.html

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.
 

AdamNC

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I haven’t calculated my daily usage in a while. I keep my dKH between 7.8-8.1 in a 29 gallon with 20 gallons volume. My auto doser doses 47ml of BRS Soda Ash a day. I have about 90% sps, a Duncan with 25 heads and a few Zoa colonies
 

Rakie

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I haven’t calculated my daily usage in a while. I keep my dKH between 7.8-8.1 in a 29 gallon with 20 gallons volume. My auto doser doses 47ml of BRS Soda Ash a day. I have about 90% sps, a Duncan with 25 heads and a few Zoa colonies

According to BRS, with a 20 gallon water volume, 14.2ml is an increase in 1 dkh. So you're dosing around 3.3 dkh per day. (Funny, I didn't notice you mentioned 20 gallons water volume, and that was around my guesstimation)

As for me, I've got around 45g water volume, and a WHOLE ton of SPS. BUT, I just switched up to LED's and everything has slowed Alk consumption, so I went from dosing around 1.3-1.5 to dosing like 0.75 for now.
 

dragon99

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I too was quite surprised how many people are on the low end of Alk consumption. Personally I'm around .75 dkH/day and feel like it should be higher considering my tank is mostly SPS. But, well, it's been pretty steady at this rate for almost the entire year.
 

jimo12

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In my 70g i dose 120ml of fauna marin 3 part baling calcium 500 and Magnesium 1500 i have full sps and lps
 

Faulkner’s maze

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Right now I am dosing sodium carbonate at about 16 ml per day to keep it in the 7.5-7.7 range on a 90 gallon tank with prob 95 gal water volume.
 

WeaveAway

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I have a 110 tank with about 8 different corals, 1 Maxima clam and some inverts. Due to a calculation error, my take was overdosed with Instant Ocean Reef Crystal salt. Salinity levels were off the meter. Began water changes adding only fresh ro water until it came down to 1. 026. Had my water tested at lfs who recommended the 2 part. Been putting in 85ml daily with buffer (1 tblsp). Checked parameters after 5 days and the alkalinity is about 16+. Stopped dosing and after 1 day it's down to 15.7. Should I add baking soda to lower it faster? And if so, how much?
Thanks.
 

Randy Holmes-Farley

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I have a 110 tank with about 8 different corals, 1 Maxima clam and some inverts. Due to a calculation error, my take was overdosed with Instant Ocean Reef Crystal salt. Salinity levels were off the meter. Began water changes adding only fresh ro water until it came down to 1. 026. Had my water tested at lfs who recommended the 2 part. Been putting in 85ml daily with buffer (1 tblsp). Checked parameters after 5 days and the alkalinity is about 16+. Stopped dosing and after 1 day it's down to 15.7. Should I add baking soda to lower it faster? And if so, how much?
Thanks.

I’m confused. Baking soda boosts alkalinity so it would not seem a suitable way to go. Muriatic acid will lower alk, but I might just let it drop on its own.m with no alk dosing.
 

WeaveAway

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Ok. No I'm the confused one here. Thought I read it the other way. As long as it continues to drop, I'll just keep an eye on it. Just hope it doesn't damage the living beings.
 

Randy Holmes-Farley

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Ok. No I'm the confused one here. Thought I read it the other way. As long as it continues to drop, I'll just keep an eye on it. Just hope it doesn't damage the living beings.

If it is still above the top end of one syringe of titrant, you can start a second syringe to get to the endpoint and add the values together. That way you can track if it is dropping as you want.
 
BRS

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  • Very important

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  • Somewhat important

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    Votes: 47 9.1%
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