ionic balance?

[Greg Grasson]

What do people mean when they refer to "ionic balance" in an aquarium? Can anyone explain this to me in a way that even Homer Simpson would understand? I've had one chemistry class in my life, back in high school, and got a D in it. I'm mainly interested in ionic balance and how it pertains to calcium, PH and alkalinity levels in the aquarium. My tank has only been set up for about a month. It's a 20 gallon, with 30 pounds of live rock, and a single clown fish. The nitrogen cycle has completed. There are 2 power heads and an empty hang on filter for circulation. I have a protein skimmer on order, but havent received it yet. I do 20% water changes each week, and was adding baking soda (about a teaspoon a week) to maintain PH, and alkalinity. All of a sudden, the PH dropped from 8.2 to about 7.7 and no matter how much baking soda I added, the PH would not go back up, although the KH increased. I was wondering if this had something to do with this "ionic balance" being screwed up from the baking soda. I have since changed all the water and everything is back to normal. I would just like to know how to keep up the PH and alkalinity without screwing the water chemistry up before I start adding any corals to the tank.

[joanadam]

Alkalinity is related to PH in that it gives the tank the ability to resist change in PH by buffering.
Corals, coraline algae, etc grow by laying down a skeleton of calcium carbonate. They do this by taking calcium and carbonate from the water and combining them into calcium carbonate. This means that these levels get depleted and need to be replaced.

Calcium carbonate will also dissolve back into calcium ions and carbonate ions. Depending on the PH Value the water reach a saturation level where the calcium ions and carbonate ions will form calcium carbonate solids, when the PH drops the water can hold more and calcium carbonate will dissolve back again. Or if the water is not saturated calcium carbonates will dissolve back to calcium ions and carbonate ions again. This means sand, rock, and even coral structures can begin to dissolve. So it is important to keep the levels saturated.
Since their is a direct relationship between calcium and alkalinity we must keep the levels of calcium ions and carbonate ions in correct ratios in order to not have an imbalance and form calcium carbonates. This is referred to as ionic balance.

Hope this clarifys it for you.

[Randy Holmes-Farley]

Sure. Seawater contains many different ions. The primary ones are sodium, chloride, magnesium, and sulfate, although there are more than a hundred others.

Fish and other organisms expect these to be in a particular ratio.

If you add something that messes with this ratio, then one could say that it was no longer ionically balanced.

People also sometimes refer to ionic balance as relating to the relative amounts of calcium and alkalinity. Again, organisms expect those to be at particular levels, and too much or especially too little of each can be a problem.

Finally, some folks use it to describe any problem with tank water that they don't knbow how to fix except with a water change. :lol:

This article describes what is in seawater:

Understanding Seawater
http://web.archive.org/web/20030620210431/http://www.animalnetwork.com/fish2/aqfm/1998/july/features/1/default.asp

As to pH, adding baking soda is not a useful way to raise pH. It actually lowers it.

My suggestion is to pick a balanced calcium and alkalinity additive system, such as one of the ones described in this article:

How to Select a Calcium and Alkalinity Supplementation Scheme
http://www.advancedaquarist.com/issues/feb2003/chem.htm

You may also find this article interesting:

Reef Aquarium Water Parameters (a summary general article)
http://www.reefkeeping.com/issues/2004-05/rhf/index.htm


and these two:

Solving Calcium and Alkalinity Problems
http://www.advancedaquarist.com/issues/nov2002/chem.htm

Solutions to pH Problems
http://www.advancedaquarist.com/issues/june2002/chem.htm

[Greg Grasson]

Thanks for the help people, that does clear things up a bit. Just out of curiosity, what happens if you boost your KH past where it's supposed to be relative to calcium, or vise versa?

[joanadam]

Then you would either have to do water changes to bring the balance back or add more calcium to form calcium carbonates.

[Randy Holmes-Farley]

Just out of curiosity, what happens if you boost your KH past where it's supposed to be relative to calcium, or vise versa?

That's right. You will get more and more precipitation of calcium carbonate (on things like heaters, pumps, sand, etc) as alkalinity, calcium, and pH rise too high. In many cases, it goes unnoticed.

[Greg Grasson]

So you're saying if you add too much buffer, even if your calcium levels are already way below where they should be, lets say 50-100 ppm., the little calcium that is in the tank will combine with the excess carbonates and precipitate out of solution as calcium carbonate? If your calcium levels are way too high, and KH is very low, will the calcium again combine with the little carbonates that are in the tank and precipitate calcium carbonate out of solution?

[Randy Holmes-Farley]

So you're saying if you add too much buffer, even if your calcium levels are already way below where they should be, lets say 50-100 ppm., the little calcium that is in the tank will combine with the excess carbonates and precipitate out of solution as calcium carbonate?

Yes, although in that scenario, you'll need to push the alkalinity very, very high to induce abiotic precipitation. In a sense, it is the multiplication product of calcium and alkalinity concentrations that is important. If that product gets high enough, precipitation will become significant.

Same with the high calcium, low alkalinity scenario: very high calcium is necessary.

I show such combinations in this article:

Calcium and Alkalinity Balance Issues
http://reefkeeping.com/issues/2002-04/rhf/feature/index.htm

[Greg Grasson]

Thanks Randy. I did read the article you wrote on calcium. Unfortunately, when you started talking about the chemical equations, I was lost. You may as well have been speaking in Swahili. That's why I figured I would ask here. But now, I think I understand what you were talking about now. All I need to do is drip kalk at a rate that maintains proper calcium and alkalinity levels, and if I notice one or the other getting too low, just add the relevant part of a balanced 2 part addititve like B-Ionic to bring the level up, correct? If I do this correctly, should my PH stay in a good range? Also, how often is it usually necessary to test for calcium and alkalinity? Those calcium test kits are friggin expensive, and you really don't get many tests out of them.

[MiddletonMark]

Originally posted by Greg Grasson
Thanks Randy. I did read the article you wrote on calcium. Unfortunately, when you started talking about the chemical equations, I was lost. You may as well have been speaking in Swahili. That's why I figured I would ask here.

Took me almost a half-dozen reads of those articles ... as until you've tested and dosed a while - some of it's over your head.

I still don't fully understand that ORP article ... but just keep it in mind, check it out every 2 months as whole sections will make sense after a while :)

Your Kalk + 2-part solution sounds pretty good. I'll let others comment more.

As for test kits - it is tough, at first. As you're stocking, your Ca/Alk demand will change ... so I ended up testing nearly weekly for the first 6-9 months ... now at maybe once a month, sometimes twice. I judged it by the fact that over 6 weeks my Ca/Alk changed very little [noted thru tests]. At that point I figured I had a schedule and demand figured out mostly - as it was being kept stable just thru practice and habit.

Anyway that's my take. It is expensive on test kits for a while ... just be glad you don't have multiple tanks:eek:

[Randy Holmes-Farley]

It wasn't so much the equations that I thought would be useful for you, as the comparative supersaturation levels of different calcium and alkalinity combinations that will lead to equal rates of abiotic precipitation.

Here are some combinations of calcium, alkalinity, and pH that have equal supersaturation with respect to aragonite:


Supersaturation = 1 (risky: dissolution of aragonite begins here)

pH = 7.7......................................pH = 8.2
Calcium = 410 ppm.....................Calcium = 340 ppm
Alkalinity = 2.5 meq/L..................Alkalinity = 1.0 meq/L

Supersaturation = 3 (typical of normal seawater)

pH = 8.2..........................pH = 8.0..........................................pH = 8.4
Calcium = 410 ppm..........Calcium = 410 ppm........................ Calcium = 260 ppm
Alkalinity = 2.5 meq/L.......Alkalinity = 4.0 meq/L ......................Alkalinity = 2.5 meq/L

Supersaturation = 6 (non-biological precipitation is more likely)

pH = 8.2................................................pH = 8.2
Calcium = 410 ppm...............................Calcium = 820 ppm
Alkalinity = 5.0 meq/L.......................... Alkalinity = 2.5 meq/L

pH = 8.0................................................pH = 8.7
Calcium = 410 ppm................................Calcium = 410 ppm
Alkalinity = 8.0 meq/L............................Alkalinity = 2.5 meq/L

pH = 8.45
Calcium = 410 ppm
Alkalinity = 4.2 meq/L

[Randy Holmes-Farley]

All I need to do is drip kalk at a rate that maintains proper calcium and alkalinity levels, and if I notice one or the other getting too low, just add the relevant part of a balanced 2 part addititve like B-Ionic to bring the level up, correct?

That is a fine way to approach the situation. The corrections might be once a month or once every 2 years or longer, depending on your pickyness and the nature of the processes in your particular aquarium.

FWIW, I'd test once every 1-4 weeks, depending on how stable things look, then let it run longer and longer. I measure calcium and alkalinity once a year or less, and usually then only to be able to say exactly what the parameters are for some experiment or other.

Anyway that's my take.

:thumbsup:

[Greg Grasson]

Randy, what do you mean when you say that these differant conditions have the same supersaturation levels?

[Randy Holmes-Farley]

That means that the tendency to precipitate calcium carbonate from the tank water is the same. So, for example, if you put a heater into each of them, it should accumulate precipitated CaCO3 at the same rate.