These osmoregulation, KH, GH, pH, hardness threads have been getting on my nerves… in a good way. Being a Chemistry/Biochemistry major, and doing my PhD in Biochemistry now, I would like to clear up a few inconsistencies in relation to the chemical nature of these terms and actually how they APPLY to life in this case, aquatic life.
So simply, all life depends on energy. We require it to say, have our muscles contract or for chemical reactions to occur. Where do we get this energy? For plants, they consume light and carbon dioxide to produce sugars. These sugars are used up through reactions to generate molecules that are high energy ie. ATP. Animals bypass the light/oxygen part (since we consume sugars) but we still need food (sugars) to make ATP. To make the ATP, cells require an electrical chemical gradient. But that’s a minor part. :P
You might know about our nervous system. How do they work? Through electricity. Where is this energy coming from? IONS. Ions are electrically-charged particles, either atoms or molecules. Ions are what create this gradient that allows for ATP production and for our nerves to communicate.
How should you think about it?
Quite simply, have you ever been shocked by static? Static is due to the fact that one object, has a positive charge and the other negative. Nature likes to equalize things and so the charges move to get both objects neutral. But what if there is a barrier in between (in electrical terms, an insulator)? That keeps the charges apart. Our cells have developed a way to do this and to CONTROL the amount of ions that pass, and harvest the charge movement for useful purposes instead of having the charges jump all at once like a static discharge.
So all this biochemistry talk, what does this have to do with our fishies?!
Well, as you all might know there has been lots of talk on osmoregulation and how BC water is inappropriate for it especially for fish. As well, lots of talk about the conditions for shrimp. Why? Because osmoregulation is the diffusion of water through a cell and its environment. Why is this important? Well everyone here has taken a bath (at least I hope). When you stay in the tub too long, what happens? Your hands and feet get pruney. That is osmoregulation at work. Your cells have a much higher salt concentration and your skin cells have little pores that allow water through. Like most things in nature, water also likes to be equalized (REMEMBER THIS PHRASE). Because there is more salt in your cells, water goes in to try to bring it down to the level it is at in a bathtub (which is not a lot). As a result your skin cells swell.
Now think about this with your fish. Imagine living in an environment like that. NOT FUN going constantly pruney. However, in their case they can’t jump out of the tub and they must ADAPT. Some fish do it better, some fish just die. The way they adapt is the cells change to balance the amount of water and ions to survive in these new water conditions.
As I mentioned, cells use ions to produce energy and to transmit messages through our nerves, amongst other things. These ions have to be a certain level for the processes to be 100%. If a fish has to adapt to conditions where there is say LOW ions (low GH/KH) and so their cells take up water because of the imbalance, this totally disrupts the internal processes that are happening within the cell. Each cell might not be able to divide, produce energy, contract, transmit a message to neighboring cell as efficiently as possible. Fine, your fish might not die, but they are certainly not optimal. They are merely surviving, not thriving. As suggested, the effects might only be seen during times of additional stress. In low ionic conditions, the fish are already adapting. Forcing another stressor makes the cells in the fish completely incapable of coping to a secondary stress.
In terms of shrimp, they experience the same things (huge losses in new tank syndrome) but they also are desperate for certain ions (mainly ones discussed to/referred in GH, or calcium, see below) Any lack of it will be detrimental.
OK you might say, I believe in the importance of ions in this superficial way. But how about the water chemistry. “Someone told me to add x to y but z changed and then x changed so I added p and then y changed” and “Someone said to add this but it didn’t help, but when I did this it helped” are all common. That is because all these processes are connected and are in a equilibrium (balance with each other).
GH is actually the EASIEST to explain. GH, general hardness, is a measure of the AMOUNT by definition of ions with two positive charges, like calcium and magnesium ions. Why two charges? That is beyond the scope here and of no consequence. Our kits use a compound that can bind these ions and produce a colour change that we take as a measure of how much ions there are. Calcium and magnesium are mainly available as salts. Why because salts are essentially ion pairs of positive and negative charges, and you cannot just get ions alone (or else they’ll come clinging on to you and never let go (remember they are charged)).
Typical GH salts are
-Calcium Chloride (CaCl2)
-Calcium Carbonate (CaCO3) (SPECIAL NOTE: for the next section re carbonate)
(note that Magnesium can take calcium’s place)
When added to water the salts split up into its negative and positive parts. In the case of calcium chloride, you will get a calcium ion (positive) and two chloride ions (negative)
The Ca(2+) AND Cl- is what is important in osmoregulation. Also involved in other processes (see above)
KH, gets a bit more complicated. KH is carbonate hardness (also termed alkalinity), and is a measure of carbonate ions. What is carbonate? It is a molecule that holds a charge (Calcium and chloride ions are charged atoms). It is also related to carbon dioxide (SHOCK) and baking soda (GASP).
Here are some formulas for those that are interested.
Carbonate + Proton < > Bicarbonate
CO3(2-) + H+ < > HCO3-
Bicarbonate + Proton < > Carbonic Acid
HCO3- + H+ < > H2CO3
Carbonic Acid < > Water + Carbon Dioxide
H2CO3 < > H2O + CO2
Carbonate + Proton < > Bicarbonate + Proton < > Carbonic Acid < > Water + Carbon Dioxide
So a few things to notice
a) bicarbonate is present in baking soda which is sodium bicarbonate (NaHCO3)
b) CO2 is carbon dioxide
Some things you might think to yourself now
1) OMG what is this proton??
2) OMG carbonic acid becomes water and carbon dioxide
3) OMG when I increase KH (carbonate) I make an acid (carbonic acid), but I don’t want acid I want alkaline!!
So might I answer
1) H+, is known as a proton. It is a charged hydrogen atom. This single ion is responsible for what we know as pH.
2) Yes, yes it does, that’s why you might have heard about pH swings when you inject CO2.
3) Don’t fret, you’re not doing that even though the compound is called an acid.
So to be more in detail
1) pH is a measure of the number of protons, H+. It is a negative logarithmic scale. Science has defined a pH of 7 as neutral. What is netural? Well, water, H2O, is composed of two components
Proton + Hydroxide < > Water
H+ + OH- < > H2O
As I mentioned oh so often before, nature likes a balance. And she likes both sides of this equation. At water’s normal equilibrium, or balance point, there is a certain amount of H+, matched by an equal amount of OH-, matched also by an equal amount of H2O.
To picture this, think of an orange, split it in half and you get both sides of the equation. Now split one of the halves into two. Now you have 2 quarters and one half. But they all add up to be two halves that are equal yet in different forms.
At this point, let me say that we can measure the amount of protons and because it is in water of a certain volume, we know its concentration. If we were to measure the number of H+ at the balance point of water, we obtain a certain concentration. In pH value, that is 7. Remember, this is a NEGATIVE LOGARTHMIC SCALE. The MORE protons you have the LOWER it gets. The LESS protons you have the HIGHER it gets. Also, to get higher or lower than 7, you must have other things that add in more protons, or take them away.
So how does carbonate hardness relate to pH? Well if you look closely at the first part of the formulas, the first line is carbonate. When we add carbonate with H+, it makes bicarbonate. As I mentioned, the amount of protons determines the concentration that determines the pH. If Carbonate uses up a proton to make bicarbonate, the amount of protons go down, and thus the pH goes (QUIZ QUESTION!!!!, correct answer is up).
That is why when we use a product like Seachem alkaline, you will ALWAYS get an accompanying pH increase.
Some might say that they never see this, that they use Seachem alkaline and their KH goes up but the pH doesn’t. I can believe that. Remember, all of this is based on using pure water and then just adding carbonate. If there are things that release more protons into the water (say ADA soil) than in pure water, that will compensate for the loss of protons that combine with carbonate to make bicarbonate.
2) So now, why does CO2 affect KH and pH?
When you inject CO2 most people notice their pH going down. WHY? Well just look at the formulas. The arrows go BOTH WAYS. And what does nature like? BALANCE. The more CO2 you put in, the equation goes backwards (termed La Chatelier principle). What does backwards give you? Carbonic acid. Now go a line up, if you have more carbonic acid, and nature loves to balance, what does that give you? More protons. What are more protons? LOWER pH. You might say, but hey, KH should go up as well. Most people don’t see this and it is mainly because 1) carbonate is converted back to carbonic acid quickly. 2) used up by plants. 3) forms other compounds with other ions.
In addition, this is why “aged” water usually has lower pH. The reason? Water from the tap are in sealed pipes. When we put it in a bucket it is exposed to the atmosphere, an environment with MUCH MUCH more carbon dioxide. This gets dissolved in water and all you have to do is look at the formulas. Some carbonic acid is produced and then just follow the arrows backwards. Theres a point where a H+ pops up by itself. What happens when there are more H+, lower pH…
In general the point is, if you are injecting CO2, some people say to have higher KH. They call this "buffering capacity" Essentially, by having carbonate present AND injecting CO2 at the same time, you are pushing the balance forward in one direction (due to carbonate) and backwards in the other (due to CO2) at the end, because of the two OPPOSING effects, your pH is more stable. This type of push/shave effect is also seen when lights are off in a tank. At night, in a planted tank, the plants stop consuming carbon dioxide and so it builds up. Because of the presence of carbonate, CO2 does not lower the pH swiftly. That is why some people turn off CO2 at night (the other reason is that it is a complete waste since your plants aren't using it since the lights are off).
3) And finally, now eventhough a line in the formulas says acid, it does not mean that will occur. In the above discussion, we are always adding the other compounds (eg carbonate or carbon dioxide) Only when we screw up the natural balance of pure water (injecting CO2, see above #2) will it make your water acidic, because you are pushing all those balances in reverse. If we add carbonate (seachem alkaline, see above #1) you are pushing those balances forward. Only when H+ is free in water does it get more acidic.
So what am I advocating? Nothing. I just needed to do this to clear the air. But I am not pushing any specific KH/GH value. Why? Because different species require different conditions. What I do know is that NOTHING can survive in pure water. There is too much variation from tank to tank to suggest anything (type of substrate for instance). The only thing I would suggest is that people not add tons of chemicals because of their test results. Things are ALWAYS in balance. The more you try to push it in one direction, the HARDER nature will push back to fix it. To finally “force” your condition in a system that does not want to be at that condition, would require so many chemicals your fish will die.