Another way to look at calcium, alk and pH


Active Member
You stand in front of you saltwater aquarium with test kits in hand. You do a series of water qualtiy tests.
What does all this mean when we measure and try to control the calcium, alkalinity and pH.
One way to think about it - although sort of screwy - is to imagine you're standing in front of an ATM machine.
When you went to the bank the very first time - to open up your accounts and get your ATM card - it's like setting up your tank for the first time and filling it with new saltwater.
Each account had "so much" money in it, based upon how the saltwater mixed up.
You do the tests on the various "accounts" in your bank.
You have
1) An account called calcium
2) An account called alkalinity
3) An account called pH
4) An account called magnesium
To have a heathy tank - you need to keep so much money in each account. But the thing is - YOU CAN NOT DIRECTLY TRANSFER money from one account to another. They are different forms of currency.
Calcium currency - we'll call ppm
Alkalinity currencty - we'll call meq/L ( or dKH )
pH currency - we'll call that pH
Magnesium currencty - call that mg/L
If you assume you opened up the bank account with the "proper" amount of currency in each account - the amounts that are most closely related to natural seawater .... then you'd have somewhere around ...
400 ppm calcium in this account
2.5 meq/L carbonates in the alk account
8.3 pH in that account
1300 mg/L magnesium in this last account
Now what happens as time goes along
Well you have some things that are going to happen "without" you doing anything.
These things are like "automatic" withdrawls.
Over time - the tankwater chemistry will change, and the amounts of currency in each account will change due to some natural reactions ( withdrawls ) that occur.
But the number of and degree to which these automatic withdrawls occur - DEPENDS ON what's in the tank, and the rules of the bank. The rules of the bank we can call CO2 carbon dioxide.
The CO2 rules are pretty much the same for all of us. Each or our banks must follow the same set of rules.
AND as the account balances move around, either going up or down, the rules will try to make some adjustments to these accounts. The bank may start "converting" some currency over to another - or combine the moneys to make different types of currency.
As you place a lot of live rock that is covered in "living" coralline algae AND you begin to place hard corals in your tank - you essentially start having more of these living organisms each making their own "automatic" withdrawl from the accounts.
The corals and coralline will start "taking" out some money from the calcium and alkalinity accounts.
The more organsims you have doing this - the faster the different types of money are removed.
As these creatures and algae continue to take out money - the rules of the bank ( CO2 ) may step in and say - nope - not going to let this happen. The rules may start saying "I'm going to step in now and change the balances around on my own".
If nothing is done to build these account balances back to where they should be ( like in natural seawater concentrations ) then the account balances get out of whack.
If the corals/coralline removes a lot of the calcium and alkalinity carbonates to form calcium carbonate - then these two separate accounts get very low. If still nothing is done - then the accounts can drop so low that the corals and coralline stops growing.
So we as the account managers must build these accounts back up by intervention. We add stuff back into the tank - just like making a deposit back to our bank accounts.
We can make these deposits several ways.
We add calcium supplements.
We add alkalinty builders.
We add pH buffers
We dose kalkwasser
We add a calcium reactor
We do water changes
But here's the tricky part. The rules of the bank are ALWAYS in place. The RULES say - that if you only add to ONE of the accounts - and do not add to the other accounts at the same time - then I being the RULES will convert some of currencies around again - and try to balance the numbers myself.
This goes on ALL THE TIME.
If you only add calcium - and keep adding calcium - that account may get too high - up over 550 ppm - then the rules say NOPE - this is not good.
The calcium will precipitate out of the tankwater, by stealing money from the alkalintity account - and will form a new currency called calcium carbonate. The tank may appear like it's snowing, or the water will get very cloudy.
When this happens - it withdrawls A LOT of the money in the alkalinity account. It's gone. The separate calcium and carbonates are no longer available cause they are a new form of money now. They are a combination of each other.
They are a solid now.
When the alkalinity account is low - the PH account begins to drop too. The alkalinity account and the pH account work together, although they are different currencies, one affects the other greatly.
Now to make things even more tricky - the pH account is very closely governed by the CO2 RULES of the bank, and any pH buffers we add.
When everything is new, and all the other accounts are pretty much in balance ... if we allow the pH to get too high - like up over 8.5, then this high pH account may prevent you from keeping the calcium account in line. The higher the pH of the tankwater - the less calcium the water will hold in solution.
Magnesium - now this account is pretty stable for the most part. Doing regular water changes normaly is enough to keep the balance of this account up around 1300 mg/L.
There are no major "automatic" withdrawls of magnesium.
Not that the magnesium does not fluctuate like the calcium/alkalinty and pH, but there are not as many automatic withdrawls going on. PROVIDING all the other accounts are kept in balance - rarely do we need to add magnesium.
But ( there's always a but )
As time goes along ....... if for some odd reason you do get an imblance between the other 3 three accounts - and you get calcium carbonate to form as a solid in the tankwater - as the calcium and alkalinity accounts drop - so does the magnesium. All four accounts are now depleted. Once this occurs - and the hard solid calcium carbonates fall out of the water ( cloudy water, white dusty looking stuff in your live rock, pumps or heater ) then it's time to get things back in balance.
The accounts are messed up bad.
If the magnesium is low - chances are very good that somewhere along the line - the alkalinity and calcium levels got out of whack.
You may have corrected for the drops in carbonates by adding buffers, you may have corrected for the drop in calcium by adding just calcium - but the magnesium account was never adjusted back up to where it should be.
Once again - what affects one WILL affect the other's.
You can try to deal with each account separately by adding supplements ..... but since all the accounts are affected by this precipitation - the best thing to do is do several water changes.
Doing several water changes over several weeks is like going back into the bank - telling the bank you're sorry you messed up your accounts so bad - and that you're willing to do water changes to get the accounts back into a better balance.
The bank is very firm in its rules - but forgiving as well.
As long as you keep your balances in check - the bank will oversee the tank and the CO2 rules will work well.
The penalty that the bank imposes on us if we don't play by the rules, and we let one or two accounts drop too low or get too high ........ white flakey stuff in our tank, uneplained cloudy water, corals not doing well, coralline may die off, pH may drop a lot, fish may die, sandy substrates may clump together, inverts may die and we as the tank caretaker stand in front of the ATM looking at the account balances reciept trying to figure out what the heck happened.
The rules are the same for everyone's tank.
Each of us have these accounts to manage.
How you manage them is your choice.
These accounts must be managed so that each of the balances are truely in "BALANCE" with each other.
Each account is in balance with the types and amounts of money in natural seawater.
But they MUST be managed by US - otherwise the bank will step in and try to do it themselves.
When the natural laws of the bank step in - sometimes it's not a pretty site.


LOL Broomer, you are da' man! When I grow up I want to be able to express myself as clearly and hopefully with one tenth the knowledge!
Thanks dude,


Active Member
LOL Paul !
Remind me to never sit down to pay bills and do water quality tests during the same morning.
I just re-read what I typed - and it's pretty crazy way to look at things :rolleyes:
Oh well - bills are paid and the tests came out pretty good again.
Happy reef'n ! and glad you enjoyed it you guys :)


Broomer, that is the craziest analogy I have ever heard someone come up with for ANYTHING, but in some strange way it all makes sense. I looks like you really put a lot of time into that. Thanks :)


Looks like one for the archives to me. Great Job Broomer! That ought to clear alot of things up for alot of people...;) Would you mind if I post that on my site, for future reference?


Active Member
You may do whatever you want with that piece of work LOL.
Seriously - if you like it you can post it - thanks.
Of all the messed up ways of looking at something - I must admit that is one goofy viewpoint.
No wonder I've struggled with this stuff.
Nurse ! I'm ready for my meds now :p
Thanks guys


I agree with blondenaso, it's a different way of putting it, but it is a really great post. I know it helped me understand the balances a lot better. Thanks Broomer.
divedog :)


This is one of the post I was refering to --for help with the other thread--thanks for looking this up


This is a great post. I wish I would have seen it when I started my reef tank.