Ph

[lduncan]

Probably the most interesting part of that extract above:

Unlike the calcium concentration, it is widely believed that certain organisms calcify more quickly at alkalinity levels higher than those in normal seawater. This result has also been demonstrated in the scientific literature, which has shown that adding bicarbonate to seawater increases the rate of calcification in Porites porites.4 In this case, doubling the bicarbonate concentration resulted in a doubling of the calcification rate. Uptake of bicarbonate can apparently become rate limiting in many corals.5 This may be partly due to the fact that both photosynthesis and calcification are competing for bicarbonate, and that the external bicarbonate concentration is not large to begin with (relative to, for example, the calcium concentration).

[Fay]

Effects of Elevated Nitrate in Aquaria

In addition to the concerns described above relating to the growth of potentially undesirable organisms that may be promoted by elevated nitrate (especially algae and dinoflagellates), corals can be impacted by nitrate. Many corals may not be bothered by elevated nitrate, or may even grow more rapidly with the readily available nitrogen. But in certain corals, especially those that calcify, there may be negative effects from elevated nitrate.

In most cases where nitrate levels have been examined in relation to the growth of calcerous corals, the effects have been reasonably small, but significant. Elevated nitrate has been shown to reduce the growth of Porites compressa (at less than 0.3-0.6 ppm nitrate),16,17 but the effect is eliminated if the alkalinity is elevated as well (to 4.5 meq/L). One explanation is that the elevated nitrate drives the growth of the zooxanthellae to such an extent that it actually competes with the host for inorganic carbon (used in photosynthesis and skeletal deposition). When the alkalinity is elevated, this competition no longer deprives the host of needed carbon.17

[Fay]

I would up your dose of prodibio/bio digest to once a week for a month. also need to add biotum to feed the bactaria in the bio digest.

? I don't use this I use Vodka

[Fay]

So after all that is it ok to carry on with the alk and don't worry about the ph or should I be testing the ph at the same time (Pies I don't use a CA reactor)

[lduncan]

Yeah you should be fine. Especially if you don't use a calcium reactor.

Gas heaters are one thing which can affect atmospheric CO2 in your house, and potentially shift the pH alkalinity balance too. So if your not running one of those, I'd say don't bother, the pH takes care of itself.

[Fay]

Gas heaters are one thing which can affect atmospheric CO2 in your house

Now your reading my mind this was going to be my next question.

I use a gas heater and leave a window by the sump open but it does worry me

[Fay]

and potentially shift the pH alkalinity balance too. So if your not running one of those

So if the heater shifts the ph alk balance is it permanent or does it move again when the heater goes off?

[lduncan]

The shift comes because the heater produces CO2 as a waste product. That means that the CO2 levels in the room rise and correspondingly the CO2 levels in the water rise, which shifts the equilibrium in the carbonate / bicarbonate system which changes the pH of the water.

So when the heater is turned off, the CO2 levels in the room will eventually go back to normal as the it defuses, which will reverse the effect, but how long it takes is dependent on a lot of other things, so it may or may not be a quick reversal.

As long as there's reasonable ventilation it should be fine. But I wouldn't get too paranoid over the pH thing.

It might be worth testing the pH to see what effect the heater has. If it's significant, you might have to do something about it. But it's not really something you need to be doing routinely.

Layton

[Fay]

[wasp]

Fay an easy way to look at it is KH raises PH, and Co2 drives it down.

That's actually a little oversimplified, but for our purposes that's a good way to look at it.

To look at it in a little more detail, KH under normal aquarium conditions raises PH to around 8.3. Then if there is too much Co2 in the water, it will drive PH down.

BUT, the more KH, ( higher dkh number ), the more Co2 there has to be to lower PH. So having a higher alkalinity will hold PH up even when there is a lot of Co2.

I should say that even that is a little simplistic but the understanding can be lost if I bog down in heaps of chemistry, that is enough to know.

The only difference between adding baking soda, and baked baking soda, is that the baking soda initially releases some Co2 into the water, dropping PH. This is only temporary as the Co2 will diffuse at the water surface & then the baking soda will cause PH to rise. Baked baking soda is the same but does not release any Co2, so will not cause a temporary dip in PH.

While there are some points in favour of running a high KH, be aware a high KH has also been shown in low nutrient systems, to be associated with RTN of SPS corals. For you at the moment a KH of 12.5 will be OK, however as you win the war on nutrients you should also lower KH and raise calcium, the correct balance between the two becomes more important the lower your nutrients.

In fact for you at the moment, there will be little advantage in running a KH anything over 11, and at this level, a calcium of 380+. However over time if the other problems you have get solved it will be preferable to move more towards NSW levels, as Reef has stated.

[lduncan]

BUT, the more KH, ( higher dkh number ), the more Co2 there has to be to lower PH. So having a higher alkalinity will hold PH up even when there is a lot of Co2.

Are you sure about this?

be aware a high KH has also been shown in low nutrient systems, to be associated with RTN of SPS corals.

That would be interesting to see. Got a link?

Layton

[wasp]

Yes.

[lduncan]

Isn't the pH swing the same?

[wasp]

Actually to be fair, I'll answer in a little more detail.

My answer was brief because I showed you a link about this already when you were arguing on it maybe a year or so ago. You just dismissed it as the guy didn't know what he was on about, much in the same way you rubbished Mesocosm recently. I think that to you, this was justified, because you think that anybody who uses Zeovit, automatically does not know what they are talking about. :roll: Then there was several pages of pointless argument which was degrading & I wish I hadn't bothered.

Doubt you have learned anything in the meantime & I can't be bothered with all that stupid argument again, it's already been done.

So, if you feel otherwise, over to you. I can guarantee if we do this all over again it will be yet another thread you are in that will be moderated, and every time I get caught up in these I wish I hadn't.

[lduncan]

:roll: I didn't rubbish Mesocosm at all:

Actually I think mesocosm has missed the point on this one. While much his information is correct, it doesn't relate to increased alkalinity.

What he is describing is a shift in equilibrium due to other environmental changes, independent of raising alkalinity.

And despite your persistent mindset I have nothing against anyone who chose to use zeovit, or any other method. I've been pretty patient with some of your snide posts recently so quit playing a victim. Most of the time I'm just asking questions. You always try to make things seem like a personal attack on you or someone else, it's not.

Back on topic, guide me to the link that you say will clear this up and i'll read it. If it doesn't clear it up, i'll do some numbers and find out what actually happens. I have a gut feeling that the pH swing will be the same irrespective of what the alkalinity is for this carbonate / bicarbonate / CO2 system.

[slappers]

http://www.fnzas.org.nz/fishroom/viewtopic.php?p=39677

[Fay]

Wasp:

Thanks for that good point yes I better keep an eye on my nitrates

P.S Frog turned the heater on this morning and I turned it off.

[Sharkey]

very interesting. I don't test for Ph but have started to add white vinegar (Acetic Acid) to my Kalk after reading this. http://www.saltcorner.com/1024/index1024.htm

Works a treat but what is it doing to my PH? I'm still doing test as my feeling is because the kalk is more soluble it will be used a lot easier. And I will have to adjust my dosing accordingly. Something eles that I found very interesting

Third, after all the cool Calcium ion chemistry is over, the leftover Acetate ions from the broken-down Vinegar leaves you with free organic Carbon in the water that feeds the bacteria in your tank so that it converts more poisonous Nitrates to NO2 gas (a very good thing).

[gregb]

If your KH is 12.5 the PH should be around 8.3.

[wasp]

Layton I was not referring to the "swing" as you call it, my concern was the relationship between KH, and Co2, and the fact that more KH will require more Co2 to drive down PH. This is more important than the temporary "swing" when introducing baking soda, which I only mentioned for the sake of completeness.

I am surprised you are not sure about this.

Also did not want to discuss further as I know you will argue. You have since proved this.

However, as you insist, perhaps this will clear it up for you. I have put into bold the part you are not sure about, but quoted a larger piece as can get very concerned about getting the whole context.

Quote "The pH of marine aquarium water is intimately tied to the amount of carbon dioxide dissolved in the water. It is also tied to the alkalinity. In fact, if water is fully aerated (that is, it is in full equilibrium with normal air) then the pH is exactly determined by the carbonate alkalinity The higher the alkalinity, the higher the pH. Figure 1 shows this relationship for seawater equilibrated with normal air (350 ppm carbon dioxide), and equilibrated with air having extra carbon dioxide as might be present in a home (1000 ppm). Clearly, the pH is lower at any given alkalinity when the carbon dioxide is raised. It is this excess carbon dioxide that leads to most low pH problems for reef aquarists.

Figure 1. The relationship between alkalinity and pH for seawater equilibrated with air containing normal and elevated carbon dioxide levels. The green dot shows natural seawater equilibrated with normal air, and the curves reflect the result that would be obtained if the alkalinity were artificially raised or lowered.

A simple way to think of this relationship is as follows. Carbon dioxide in the air is present as CO2. When it dissolves into water, it becomes carbonic acid, H2CO3:

3. CO2 + H2O à H2CO3

The amount of H2CO3 in the water (when fully aerated) is not dependent on pH, but only on the amount of carbon dioxide in the air (and somewhat on other factors, such as temperature and salinity). For systems not at equilibrium with the air around them, which includes many reef aquaria, the aquarium can be thought of "as if" it were in equilibrium with a certain amount of CO2 in the air, which is effectively defined by the amount of H2CO3 in the water. Consequently, if an aquarium (or the air it is being equilibrated with) has "excess CO2" in it, that means that it has excess H2CO3. This excess H2CO3, in turn, means the pH will fall, as shown below.

Seawater contains a mixture of carbonic acid, bicarbonate, and carbonate that are always in equilibrium with each other:

4. H2CO3 ßà H+ + HCO3- ßà 2H+ + CO3--

Equation 4 shows that if an aquarium has excess H2CO3, some if it dissociates (breaks apart) into more H+, HCO3-, and CO3--. Consequently, because of this extra H+, the pH will be lower than if there were less CO2/H2CO3 in it. If seawater has a huge excess of CO2, the pH can be as low as pH 4-6. Equilibrating my aquarium water with carbon dioxide at 1 atmosphere resulted in a pH of 5.0, although that low a value would be unlikely to be attained in a reef aquarium as the substrate and coral skeletons would buffer it as they dissolved. My aquarium water in equilibrium with 1 atmosphere of carbon dioxide and excess solid aragonite (a crystalline form of calcium carbonate that is the same form present in coral skeletons) resulted in a pH of 5.8. End quote"

Please don't accuse me of being snide or any such inflamatory stupidity, I have posted this to help you.

[lduncan]

What you posted makes sense but this is what you said:

BUT, the more KH, ( higher dkh number ), the more Co2 there has to be to lower PH.

From what I understand from that, you are saying that if your tank alkalinity is higher than someone else's, then for a given amount of added CO2 you'll get a smaller change in pH (swing was probably the wrong word to use before).

That's the part i'm not so sure on when the majority of the buffering in our tanks comes from carbonate / bicarbonate. Here's the reason. The equilibrium equations for the CO2/carbonate/bicarbonate system are:

[HCO3(-)] [ H(+)] / [H2CO3) = 10^ -6.3

[CO3(2-)] [ H(+)] / [HCO3(-)] = 10^-10.3

[H2CO3] = 10^-1.5 P(CO2)

Rearranging these you get:

[H(+)] = 10^-1.5 * 10^-6.3 * 10^-10.3 * P(CO2) / [CO3(2-)]

and pH = -log( [H(+)] )

It seems that from this, that although the pH values a different, the change in pH for a given addition of CO2 is independent of the alkalinity.

It seems that a higher KH (by adding baking soda) does not reduce the change in pH from CO2 additions, as you would typically expect from a buffer solution. I think it's a condition specific to the carbonate system and CO2, it doesn't work where the buffering capacity is provided by other ions like phosphate or boron. They behave as you have suggested.

That's why I asked the question. The passage above doesn't address that. I've asked Randy to have a look over it and see what he thinks.

[reef]

It all depends if the rate of the Kh is passive base on the equilibrium of the cronoside. The fluctuations will vary in terms of the number neutrons.

do we have a supa advance section yet

[wasp]

Layton, get over it.

[lduncan]

Do you have anything useful to add?

[lduncan]

Looks like I found the answer. This graph from Randy seems to confirm my thinking above:

The red arrows have been added by me. This shows that for typical ranges of alkalinity, a tank with a higher alkalinity (Tank 2 = 3.5) sees the same drop in pH as one with a lower alkalinity (Tank 1 = 2.5) when a certain amount of CO2 is added.

Then if there is too much Co2 in the water, it will drive PH down.

BUT, the more KH, ( higher dkh number ), the more Co2 there has to be to lower PH.

So it seems that this isn't correct in the case of CO2. So it's kind of unusual, but at the same time important as CO2 is the acid which often effects this equilibrium, and has potential to skew it.

Layton