Daily KH drop

[SquareFace]

I dose Alkalinity over night. I test it every morning and every night to fine tune my dosing pump. The KH is about 11 dkh early in the morning and about 9 dkh at the end of the day. So, it drops about 2 dkh during the day, every day. What kind of drop in KH do you experience in your tank daily?


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[dannyp02908]

if I were you, I would dose twice a day. Alk swings are not good.

 

[SquareFace]

How much does your KH drops in a day?


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[letoan]

I dose Alkalinity over night. I test it every morning and every night to fine tune my dosing pump. The KH is about 11 dkh early in the morning and about 9 dkh at the end of the day. So, it drops about 2 dkh during the day, every day. What kind of drop in KH do you experience in your tank daily?


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What's your calcium?

 

[cilyjr]

My alk does not move much ever! I sit at about 9.6 to 10.2 dkh. When it's gone higher in the past I would experience STN issues. By higher I mean 9 to 13...

 

[SquareFace]

My Ca is 420 ppm.


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[dannyp02908]

I don't know what mine drops by, I have a CaRx. Pretty stable.

 

[Andy V]

The first problem is that you should be testing at the same time everyday or else you will incorrectly measure your daily alk and calc usage. This is because the pH drops overnight (due to changes in biological activity in the water), which means your alk will test lower in the morning (because of the lower ph) than it will at night (i.e., after the lights have been on), with no other changes. You also need to be aware that your salinity and water temperature also affect your alkalinity level.

Ideally, you would test at the same time everyday, after the lights have been on for a few hours. Then you will begin to get a more accurate measure of how much alk/calc your tank is consuming in a day. The amount your tank consumes will depend on various factors, like tank size, corals in the tank, and the starting level of the alk (because the alk drop is not linear, i.e. it changes faster at different levels).

Answering your question about how much other's tanks are consuming per day doesn't matter to you, because every tank is different and it won't really tell you anything.

 

[SquareFace]

It's helpful to know that alkalinity level could be affected by PH, salinity and temperature.
My system runs the sump/refugium's lights at the time that the display tank lights are off. Keeping photosynthesis constant not allowing carbon dioxide to build up and lower the PH. So, my system's PH is perfectly constant 24 hrs a day. Salinity is kept stable by my auto top off system. And I set up my chiller and heaters in a narrow temperature range to keep it from swinging much. This means that the difference between the results of the KH tests I perform every morning at the same time and every night at the same time is not due to these factors.

The idea that knowing what happens on other's tanks doesn't matter to me because every tank is different is the answer that I get for most questions I ask at Boston Reffers.






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[cilyjr]

This is because the pH drops overnight (due to changes in biological activity in the water), which means your alk will test lower in the morning (because of the lower ph) than it will at night (i.e., after the lights have been on), with no other changes. You also need to be aware that your salinity and water temperature also affect your alkalinity level.

Incorrect...
ph and water temp do not effect alkalinity. Alkalinity is just a measure of waters ability to neutralize acid. Alkalinity DOES effect ph.

"Total Alkalinity is measured by adding a strong acid until all the anions listed above are converted to uncharged species. The total alkalinity is not affected by temperature, pressure, or pH, though the values of individual constituents are, mostly being conversions between HCO3- and CO32-."

Ph will change as the respiration of certain organisms throughout out the day changes. The ph swing is produced by excess co2 at night. The addition of alkalinity at night can help make a ph swing smaller as the excess co2 acidifies the water but the increased alk allows the solution to neutralize more acid so the swing is slighter. The same effect could be produced by increased aeration.

 

[letoan]

It's helpful to know that alkalinity level could be affected by PH, salinity and temperature.
My system runs the sump/refugium's lights at the time that the display tank lights are off. Keeping photosynthesis constant not allowing carbon dioxide to build up and lower the PH. So, my system's PH is perfectly constant 24 hrs a day. Salinity is kept stable by my auto top off system. And I set up my chiller and heaters in a narrow temperature range to keep it from swinging much. This means that the difference between the results of the KH tests I perform every morning at the same time and every night at the same time is not due to these factors.

The idea that knowing what happens on other's tanks doesn't matter to me because every tank is different is the answer that I get for most questions I ask at Boston Reffers.






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To answer your question. When I still have my 125, 65 sump with quite a bit of stony animals in there, my dkh will drop around 0.5-0.6 in 24 hours. I dose around 100ml everyday (BRS soda ash recipe) by have it drip slowly over the sump.

Don't mind if I ask, is there a reason you want to keep your dkh at 11? To steady ph?

The whole reason why I asked about your calcium because I think your mag/cal/alk is not balance and you did answer to that on post #6. Try to balance it out first and see if your daily dkh still drop at that rate.

 

[SquareFace]

According to the Reef Chemistry Calculator by JDieck. The balanced amount of calcium for 9 dkh of alkalinity would be about 425 ppm of calcium. Since my tank is at 11 dkh in the morning and 9 at the end of the day, I wasn't sure if I should balance with the higher or lower KH.



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[SquareFace]

Incorrect...
ph and water temp do not effect alkalinity. Alkalinity is just a measure of waters ability to neutralize acid. Alkalinity DOES effect ph.

"Total Alkalinity is measured by adding a strong acid until all the anions listed above are converted to uncharged species. The total alkalinity is not affected by temperature, pressure, or pH, though the values of individual constituents are, mostly being conversions between HCO3- and CO32-."

Ph will change as the respiration of certain organisms throughout out the day changes. The ph swing is produced by excess co2 at night. The addition of alkalinity at night can help make a ph swing smaller as the excess co2 acidifies the water but the increased alk allows the solution to neutralize more acid so the swing is slighter. The same effect could be produced by increased aeration.

That's what I thought. Thanks for clarifying that.


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[SquareFace]

To answer your question. When I still have my 125, 65 sump with quite a bit of stony animals in there, my dkh will drop around 0.5-0.6 in 24 hours. I dose around 100ml everyday (BRS soda ash recipe) by have it drip slowly over the sump.

Don't mind if I ask, is there a reason you want to keep your dkh at 11? To steady ph?

The whole reason why I asked about your calcium because I think your mag/cal/alk is not balance and you did answer to that on post #6. Try to balance it out first and see if your daily dkh still drop at that rate.

I'm trying to keep KH high to encourage accelerated coral growth.



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[cilyjr]

I drip Kalk slowly all day. I think Danny said it best. You might want to drip more often. If you have a dosing pump it should be easy.

 

[letoan]

According to the Reef Chemistry Calculator by JDieck. The balanced amount of calcium for 9 dkh of alkalinity would be about 425 ppm of calcium. Since my tank is at 11 dkh in the morning and 9 at the end of the day, I wasn't sure if I should balance with the higher or lower KH.



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You raise it to where you want to maintain. Before you touch cal/alk, you need to get mag to the right level first.

 

[Andy V]

Incorrect...
ph and water temp do not effect alkalinity. Alkalinity is just a measure of waters ability to neutralize acid. Alkalinity DOES effect ph.

"Total Alkalinity is measured by adding a strong acid until all the anions listed above are converted to uncharged species. The total alkalinity is not affected by temperature, pressure, or pH, though the values of individual constituents are, mostly being conversions between HCO3- and CO32-."

Ph will change as the respiration of certain organisms throughout out the day changes. The ph swing is produced by excess co2 at night. The addition of alkalinity at night can help make a ph swing smaller as the excess co2 acidifies the water but the increased alk allows the solution to neutralize more acid so the swing is slighter. The same effect could be produced by increased aeration.

I am sorry, but you are not correct. Read the following articles by Randy, a Harvard phd in chemistry and legend in the hobby...he disagrees:

http://www.advancedaquarist.com/2002/5/chemistry

http://www.reefkeeping.com/issues/2004-09/rhf/

There is a dynamic relationship between CO2, pH, and alk. You said yourself that excess CO2 causes an alk swing, so I am not sure how you basically agreeing with me makes me incorrect? Perhaps all this talk of ocean acidification from excess C02 in the atmoshopere is wrong? Low alk can cause low pH, but excess CO2, ie. low pH can cause low alk too. If your tank was in a room with no oxygen, you could add as much alk as you want to your tank, and the alk won't stay in solution.

As far as temp goes, here is something from the NOAA, which seems to disagree with you (see page 7):

ftp://ftp.glerl.noaa.gov/publications/tech_reports/glerl-139/tm-139.pdf

http://www.reefcentral.com/forums/showthread.php?t=1720735

The temperature matters because it affects your salinity reading. Your salinity affects your alk, calc, and magnesium levels. If you read a salt mix container, you would see that. If you are adding the wrong amount of salt because your temperature is inconsistent, you will add too much or too little, and your alk readings will swing.

 

[reefstarter]

I can almost tell what my alk level is by checking the PH For example if my PH is say 8.2 I know that my alk is around 8.5- 9 when the PH goes higher the alk is usually lower and vica versa it holds pretty steady , but I will be switching to dosing soon from a reactor so I can be a bit more precise

 

[Andy V]

I may be getting this backwards...let me do more reading...

 

[SquareFace]

You raise it to where you want to maintain. Before you touch cal/alk, you need to get mag to the right level first.

My Mg is 1350 ppm.


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