Can someone explain alkalinity ??? Experts help !!

[Oceanman5]

Hello R2R,

I’ve read around that alkalinity is the ability to buffer pH swings or something like that.
What exactly does that mean?
Does that mean that higher ALK is better and more resistant to pH swings.
I’m confused because I have DKH of 11 and my pH is stuck at 7.9, I thought it would easily be over 8.0

What levels of Alk become dangerous?
What are ways to increase or decrease Alk?

 

[Oceanman5]

My parameters today

 

[KStatefan]

https://www.reefkeeping.com/issues/2002-04/rhf/feature/index.php

Chemistry And The Aquarium: The Relationship Between Alkalinity And pH

Randy answers many questions in this complex relationship.

reefs.com

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

 

[nereefpat]

I’ve read around that alkalinity is the ability to buffer pH swings or something like that.

Alkalinity is the capacity of water to resist downward changes in pH. For our reefs, it is also our way of measuring carbonate which our corals use for growth.

Does that mean that higher ALK is better

It's good to target a stable number somewhere in the 7-10 dKH range. The ocean is closer to 7, but some reefers keep their tanks higher.

and more resistant to pH swings.

Downward changes, yes.

I’m confused because I have DKH of 11 and my pH is stuck at 7.9, I thought it would easily be over 8.0

pH in our aquarium is a function of only 2 things, alkalinity and CO2. So you can have high CO2 in your house that can keep pH down even if you have high alk. There is also the issue of accurately measuring pH.

What levels of Alk become dangerous?

I wouldn't want it anywhere over 9 or so. Some people keep it higher.

What are ways to increase or decrease Alk?

Increase by dosing either carbonate, like baking soda (bicarb) or baked soda (carbonate), or dosing OH like in limewater/kalk or a strong base, or using a calcium reactor.

Decrease by letting it fall over time, doing water changes with a lower alk salt, or adding an acid. Don't add acid to a tank with any animals, but some people will do this to their makeup water change water.

 

[Oceanman5]

Alkalinity is the capacity of water to resist downward changes in pH. For our reefs, it is also our way of measuring carbonate which our corals use for growth.

It's good to target a stable number somewhere in the 7-10 dKH range. The ocean is closer to 7, but some reefers keep their tanks higher.

Downward changes, yes.

pH in our aquarium is a function of only 2 things, alkalinity and CO2. So you can have high CO2 in your house that can keep pH down even if you have high alk. There is also the issue of accurately measuring pH.

I wouldn't want it anywhere over 9 or so. Some people keep it higher.

Increase by dosing either carbonate, like baking soda (bicarb) or baked soda (carbonate), or dosing OH like in limewater/kalk or a strong base, or using a calcium reactor.

Decrease by letting it fall over time, doing water changes with a lower alk salt, or adding an acid. Don't add acid to a tank with any animals, but some people will do this to their makeup water change water.

wow thank you so much, great great response

 

[Formulator]

I think you already got a great response from @nereefpat, but I wanted to add my 2-cents reading between the lines a bit… pH of 7.9 is absolutely fine. The key is consistency and not letting it drop below 7.7 which will start to dissolve coral skeletons and prevent growth. Chasing a specific high pH number often leads to more harm than good, especially with bottled additives and raising Alk too high in a new tank which can lead to precipitation of calcium carbonate on your pumps, sand bed hardening, and water cloudiness, along with general stability issues. If you really want to get pH up, you can try to increase water flow at the surface for more gas exchange, but beyond that I would caution against chasing pH with chemistry.

 

[PharmrJohn]

There is some evidence that a higher ALK (around 11) and a pH of about 8.2 or 3 will maximize coral growth. You may see this on the Internet. And it's fine if you want to try it, but I would wait until you are VERY comfortable dosing before you tackle it. It's all about stability and husbandry. And with numbers like that, it's easy to go over and do some damage (or just create a situation whereby you feel like you've got to do something NOW, NOW, NOW!