Cant keep up with my Alkalinity needs - help

ApoIsland · Feb 7, 2022

Lavey29 said:
So the poster above stating he has run a mixed reef tank successfully for years with 4 to 5DKH? Does he have a 5 PH to?

I have not tested PH in 10 years but the tank is next to an open window and a good cross breeze so I would imagine it is not low.

Rockyreef · Feb 7, 2022

So perhaps you already know this but you have to space your calcium and alk dosing apart (timewise). The alk is a negative ion and the calcium is a positive ion. If you dose too close together they will react and form a cement that just deposits on your sand or rocks without staying in solution.
I learned this the hard way...I was dosing calcium and alk like crazy and couldn't get either one to rise. But I was only dosing 5 minutes apart. Also my sand bed was turning to cement. Then I switched my interval to about 60 minutes apart and within a week my levels were sky high. I'm now dosing only about 10% of what I was and my levels are right where I want them.

Donavon · Feb 7, 2022

rhostam said:
Chemistry And The Aquarium: The Relationship Between Alkalinity And pH

Randy answers many questions in this complex relationship.

reefs.com

Thanks, that’s a long read, I will dig in tomorrow, I appreciate the info

mdb_talon · Feb 7, 2022

ApoIsland said:
I didn't do the math correctly my first time either. I errored in the opposite direction you did though and I'm amazed I didn't crash the tank.

I was supposed to add 1.5 - 2 dkh per day but instead was adding 3-4 dkh per day. Went from 5.5 to 17.5 in the course of 2 weeks. Amazed nothing died. So lucky I had a morning free and decided to just run an alk test to kill some time. I think another week of going at the rate I was and it would have been disaster.

Haha glad it all lived. When i screwup like that i call it an experiment in the name of science.

Donavon · Feb 7, 2022

Rockyreef said:
So perhaps you already know this but you have to space your calcium and alk dosing apart (timewise). The alk is a negative ion and the calcium is a positive ion. If you dose too close together they will react and form a cement that just deposits on your sand or rocks without staying in solution.
I learned this the hard way...I was dosing calcium and alk like crazy and couldn't get either one to rise. But I was only dosing 5 minutes apart. Also my sand bed was turning to cement. Then I switched my interval to about 60 minutes apart and within a week my levels were sky high. I'm now dosing only about 10% of what I was and my levels are right where I want them.

I will be mindful of this, thanks

ApoIsland · Feb 7, 2022

mdb_talon said:
Haha glad it all lived. When i screwup like that i call it an experiment in the name of science.

Very true. When you add the regent and instead of the normally purplish hue you get a very blue color you have that immediate oh crap moment. Then the 17.5 shows up on the hanna a few seconds later and you nearly soil your drawers.

Grumblez · Feb 8, 2022

mdb_talon said:
These are not accurate statements. A drop in PH does not cause a drop in alkalinity. A drop in alkalinity can cause a drop in PH but not the other way around.

Umm I'm fairly certain your backwards. Its the drop in PH causes the carbonate to transistion to bicarbonate.

For OP heres a really good video in addition to that article.

mdb_talon · Feb 8, 2022

Grumblez said:
Umm I'm fairly certain your backwards. Its the drop in PH causes the carbonate to transistion to bicarbonate.

For OP heres a really good video in addition to that article.

Where in the video backs up your claim i dont want to watch 40 minutes lol. For what it is worth i am sticking with Randy .

Post in thread 'alk dropping.. not sure why' https://www.reef2reef.com/threads/alk-dropping-not-sure-why.655429/post-6604474

Lavey29 · Feb 8, 2022

mdb_talon said:
These are not accurate statements. A drop in PH does not cause a drop in alkalinity. A drop in alkalinity can cause a drop in PH but not the other way around.

There is most certainly a connection with low PH and unstable alkalinity.

mdb_talon · Feb 8, 2022

Lavey29 said:
There is most certainly a connection with low PH and unstable alkalinity.

Based on what exactly? The alkalinity is the buffer and helps keep ph stable. A low alkalinity can make PH less stable bit the reverse is not true. PH is determined by alkalinity and co2....those are your variables for PH.

Lavey29 · Feb 8, 2022

mdb_talon said:
Based on what exactly? The alkalinity is the buffer and helps keep ph stable. A low alkalinity can make PH less stable bit the reverse is not true. PH is determined by alkalinity and co2....those are your variables for PH.

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

mdb_talon · Feb 8, 2022

Lavey29 said:
http://www.reefkeeping.com/issues/2004-09/rhf/

So where does it say that a drop in ph leads to a drop in alkalinity? I see a lot there mentioning a change in alkalinity impacts PH but nothing that says a drop in PH causes a drop in alkalinity. Maybe @Randy Holmes-Farley can shed some light since it is his article.

Lavey29 · Feb 8, 2022

mdb_talon said:
Based on what exactly? The alkalinity is the buffer and helps keep ph stable. A low alkalinity can make PH less stable bit the reverse is not true. PH is determined by alkalinity and co2....those are your variables for PH.

One of Randy's statements in another thread:

It is true that formation of calcium carbonate tends to lower pH by removing carbonate (lowering alkalinity). By Le Chatlier's Principle, removing carbonate lowers pH by causing a bicarbonate to split into H+ and CO3-- to partly replace the lost carbonate.

mdb_talon · Feb 8, 2022

So that quote is saying that lowering alkalinity lowers ph. That is what i have agreed with all along. However that is not the same thing as saying that lowering ph lowers alkalinity.

For example you can inject co2 into an aquarium and ph will drop and alkalinity remain stable.

That is not to say there are not some things that can impact both ph and alkalinity, but that does not mean that the change in ph is what drives the change in alk.

Lavey29 · Feb 8, 2022

Is there a direct and/or indirect relationship between PH and alk in a reef tank? Can one affect the other either directly or indirectly?

It's a simple yes or no question?

Grumblez · Feb 8, 2022

mdb_talon said:
So that quote is saying that lowering alkalinity lowers ph. That is what i have agreed with all along. However that is not the same thing as saying that lowering ph lowers alkalinity.

For example you can inject co2 into an aquarium and ph will drop and alkalinity remain stable.

That is not to say there are not some things that can impact both ph and alkalinity, but that does not mean that the change in ph is what drives the change in alk.

I only remember enough of Chemistry as it pertains to my everyday job (respiratory therapy). But it's my understanding that as the alkalinity buffers any acids etc it uses it up.

"Also carbon dioxide from animal respiration (Water-H2O and Carbon Dioxide - CO2 form to produce Carbonic acid) which can make the water more acidic. KH or Alkalinity absorbs these acids so that pH in an aquarium is not compromised. If over a period of time, the alkalinity gets used up (by absobing acids)"

Redirect Notice

www.google.com

I suppose that's maybe an oversimplified explanation and maybe a decrease in PH doesn't Always lead to a decrease in KH depending on cause?

Randy Holmes-Farley · Feb 8, 2022

Lavey29 said:
Is there a direct and/or indirect relationship between PH and alk in a reef tank? Can one affect the other either directly or indirectly?

It's a simple yes or no question?

Is it?

Seems like a very complex question to me, if you want to understand the ways and degrees of impact, but there are many interrelationships between alk and pH in a reef tank.

That said, one should not insinuate that IF the pH changes, that alk must change. That is not true.

One can take seawater and add or remove CO2 by aeration, and that process alone changes pH but not alkalinity.

mdb_talon · Feb 8, 2022

Grumblez said:
"Also carbon dioxide from animal respiration (Water-H2O and Carbon Dioxide - CO2 form to produce Carbonic acid) which can make the water more acidic. KH or Alkalinity absorbs these acids so that pH in an aquarium is not compromised. If over a period of time, the alkalinity gets used up (by absobing acids)"

Based off my understanding I would suggest that is wrong.

See the link for the full thread, but pasted a response from that thread here also.

Effect of CO2 on alkalinity? - Reef Central Online Community

Effect of CO2 on alkalinity? The Reef Chemistry Forum

www.reefcentral.com

----- Below is a response from that thread not my words I am not that smart
Alkalinity Facts
There are several facts about total alkalinity that follow directly from the definition. Unfortunately, some of these have been misunderstood by some hobby authors.

One of these facts is termed The Principle of Conservation of Alkalinity by Pankow ("Aquatic Chemistry Concepts", 1991). He shows mathematically that the total alkalinity of a sample CANNOT be changed by adding or subtracting CO2. Unfortunately, there is an article available on line, which claims otherwise, and encourages people to "lower alkalinity" by adding CO2 in the form of seltzer water. This is simply incorrect.

Forgetting the math for the moment, it is easy to see how this must be the case. If carbonic acid is added to any aqueous sample with a measurable alkalinity, what can happen?

Well, the carbonic acid can release protons by reversing equations 1 and 2:

(5) H2CO3 ==> H+ + HCO3-

(6) HCO3- ==> H+ + CO3--

These protons can go on to reduce alkalinity by combining with something that is in the sample that provides alkalinity (carbonate, bicarbonate, borate, phosphate, etc). However, for every proton that leaves the carbonic acid and reduces alkalinity, a new bicarbonate or carbonate ion is formed that adds to alkalinity, and the net change in total alkalinity is exactly zero. The pH will change, and the speciation of the things contributing to alkalinity will change, but not the total alkalinity.

This is not true for strong acids, however. If you add hydrochloric, sulfuric or phosphoric acids (or any acid with a pKa lower than the carbonic acid endpoint), there will be a reduction in the alkalinity.

Randy Holmes-Farley · Feb 8, 2022

Grumblez said:
I only remember enough of Chemistry as it pertains to my everyday job (respiratory therapy). But it's my understanding that as the alkalinity buffers any acids etc it uses it up.

"Also carbon dioxide from animal respiration (Water-H2O and Carbon Dioxide - CO2 form to produce Carbonic acid) which can make the water more acidic. KH or Alkalinity absorbs these acids so that pH in an aquarium is not compromised. If over a period of time, the alkalinity gets used up (by absobing acids)"

Redirect Notice

www.google.com

I suppose that's maybe an oversimplified explanation and maybe a decrease in PH doesn't Always lead to a decrease in KH depending on cause?

Simply wrong.

There is an actual chemical principle that shows it to be wrong:

Chemistry and the Aquarium: What is Alkalinity?

Randy provides an overview of alkalinity as to why it's important, how it's measured, and how can it be tested.

reefs.com

Alkalinity Facts
There are several facts about total alkalinity that follow directly from the definition. Unfortunately, some of these have been misunderstood by some hobby authors.

One of these facts is termed The Principle of Conservation of Alkalinity by Pankow (“Aquatic Chemistry Concepts”, 1991). He shows mathematically that the total alkalinity of a sample CANNOT be changed by adding or subtracting CO2. Unfortunately, there is an article available on line, which claims otherwise, and encourages people to “lower alkalinity” by adding CO2 in the form of seltzer water. This is simply incorrect.

Forgetting the math for the moment, it is easy to see how this must be the case. If carbonic acid is added to any aqueous sample with a measurable alkalinity, what can happen?

Well, the carbonic acid can release protons by reversing equations 1 and 2:

(5) H2CO3 ==> H+ + HCO3–

(6) HCO3– ==> H+ + CO3—

These protons can go on to reduce alkalinity by combining with something that is in the sample that provides alkalinity (carbonate, bicarbonate, borate, phosphate, etc). However, for every proton that leaves the carbonic acid and reduces alkalinity, a new bicarbonate or carbonate ion is formed that adds to alkalinity, and the net change in total alkalinity is exactly zero. The pH will change, and the speciation of the things contributing to alkalinity will change, but not the total alkalinity.

This is not true for strong acids, however. If you add hydrochloric, sulfuric or phosphoric acids (or any acid with a pKa lower than the carbonic acid endpoint), there will be a reduction in the alkalinity.