So, my husband swears that alkalinity and pH are the same thing. His sicence background gave me a 100% garantee. This is his argument for not getting an alkalinity tester...husbands... After all of the reading I have done, obviously I've figured out they are different, but he will just not listen to me. So, I need your help.  Without insulting (I don't want to sleep on the couch) please scientifically explain to him why pH and alkalinity are different. I would greatly appreciate it, plus I get to say, I told you so!

Sarah Lowry

PM's or emails are fine too

pH is a measure of hydronium ions (H3O+ or more commonly refered to as H+) in an aqueous solution.  Hydronium is related to hydroxide via water.

H2O = H+ + OH-

pH=-log([H+])

This is where his confusion likely comes from.  A pH of 7 is said to be neutral.  pH less then 7 is acidic.  pH greater then 7 is alkaline.  Alkaline describes a pH condition.

Alkalinity is a measure of ions in solution that collectively cause the solution to be alkaline.  So... alkalinity does not equal alkaline.

There is another property of water that is called acidity.  It is the measure of ions that contribute to the acidic nature of a solution.  Since seawater has almost no acidity, it's not important for us, but for some freshwater systems it is.

My advice for presenting this to him:  explain it to him about 5 minutes after the two of you crawl into bed.  His attention will be on sleep or something else and I find that I'm more receptive to new ideas in either of these condtions. 

Thank you so much!  I'll be sure to send this on to him.  And thanks for the communication suggestion Jon.

Sarah Lowry

How does a Calcium Reactor work to effect: 

• pH
• alkalinity
• calcium level

Does a calcium reactor completely replace dosing?

How does a Calcium Reactor work to effect: 

• pH
• alkalinity
• calcium level

pH will tend to decline due to all the CO2.  Alkalinity and calcium level should stay steady (thats the whole reason to have a reactor).

Does a calcium reactor completely replace dosing?

It can completely replace calcium and alkalinity dosing.  Other stuff may or may not need dosing.

Jon, I was told that PH will follow alkalinity.  So if your alkalinity is in an exceptable range more than likely your ph will be as well. What is your opinion on this?

It's generally true that a tank with a higher alkalinity will also have a higher pH, but really depends on the tank.  But both alkalinity and dissolved CO2 effect saltwater pH.  So if you have a tank with excessive amounts of CO2 (many tanks with calcium reactors and poor gas exchange or high indoor CO2 levels), you could have a high alkalinity and low pH.  My tank runs with 3-3.5 meq/l alk but a pH of only 7.8 - 8.0 due to CO2.

There. Now it's clickable

http://www.advancedaquarist.com/issues/may2002/chem.htm - http://www.advancedaquarist.com/issues/may2002/chem.htm

FYI - I was ready to duke it out about this as well.  With my nursing background, I was sure that alkalinity was a pH measurement.  Jon set me straight as well.

Thanks Jon for your expertise.  You are loved.

So...without a doubt you should be testing both pH AND alkalinity?  I sent him the info Jon wrote but then he said he didn't see why we had to test for both.  But you are saying it's possible to have one at a good level and one at a bad level at the same time? So testing both is necessary. Just want to finish clearing this up with the hubby.  Thank you for all of your help.

Sarah Lowry

Yes, you need to test both.  Most would agree testing alkalinity is more important.  Unless you are running something unusual (ozone, CO2, etc) you won't have many changes in pH and really don't need to test it but every once in a while.  Alkalinity is something you need to monitor, especially in reef aquariums.

I agree with Jon, anything said while in bed is either shrugged off or easily accepted.

Adam

Absolutely, pH and alkalinty are two different animals.

pH = the amount of H+ ions floating around in the water

Alkalinity = the amount of CO3++ and HCO3+ floating around in the water

Monitoring and maintaining alkalinity is more of a concern then pH.  My alkalinity can drop from 3.5 to 1.5 meq/l and only show a drop of about 0.1 pH units.  Acros are severely stressed at an alkalinity of 1.5 meq/l.

amorgenegg, yes... but with some caveats.