Are there other sources in our systems where CO3 ions can be taken such as aragonite sand? If so then the addition of just Ca ions would not affect the pH/Alk.
This is a very interesting topic and right about now I really want to go talk to one of the Chem professors or marine biology professor to really explain this once and for all.
sif, actually when the lights go off, photosynthesis does not stop, only the light requiring parts of photosynthesis stop, the plants and animals in our tanks also have a dark phase of photosynthesis, and the end product of this is oxygen to a small degree but not to the degree that it is produced during the light phase. the dark phase is more concentrated on producign ATP and stored sugars, which ourt animals metabolize and use for energy!~sorry to get off topic, i was discussing photosynthesis with my sophmore bio class today!
and this thread rocks, very genuine and very helpful. the only thing that i can think to compare a sw aquarium to is ourselves. the human body is constantly trying to reach a state of homeostasis, where all our levels are stable, not perfect, but stable, and this keeps us in a fairly good state of health. when we get sick, or injured, it throws our bodies out of homeostasis and we suffer as a consequence. this is what we must try to achieve and maintain in our little experiments called tanks; a manageable level of homeostasis. conditions will swing and levels will rise and fall, but as long as we can keep all of these thing dancing in sync together, we will be providing the best home for the animals which were once plucked form the sea.
sorry to wax philosophic but i just have a passion for this stuff, as i hope most all of us do, thus the reason for this board!
Photosynthesis, assimilation and polymerization all three related and perhaps topic for another discussion (one I will never get involved with )
Suffice to say however the PH swing at night is caused by the slowing of photosynthesis ? yes?
It's my guess that the pH swings from day to night ( tank lights on tank lights off ) is due to;
Fish respire - take in oxygen - give off CO2
They're at rest ( most of them ) when the lights are off.
How this affects the amount of CO2 - not sure.
Algae and plants - When lights are on they are taking in CO2 and giving off O2.
When the lights are off - they are not taking in as much CO2, and the natural levels of this souble gas increases from water/air interface at the water surface, or other gas echange areas of the tank.
There's more CO2 at night because these plants are not consuming it as much - and the CO2 gas concentration increases.
More CO2 = more carbonic acid = lowering of the pH.
Any wavemakers or pumps that we have on timers - may kick off at night ( the old I'm going to let my fish rest syndrome ) and as the water circulation changes - so does the gas exchange at the suface.
Bacteria do follow an active/resting cycle as well.
I'm pretty sure they take in O2 and give off CO2 - at least the aerobic ones would.
oh god look what i did i had to go and mention photosynthesis, and now all hell is breaking loose!
dont get me wrong here, the major misconsception in bio is that the dark phase of photosynthesis takes place in the dark. not true. even during the day, the dark phase is occuring at the same time that the light phase is. at night however, the light phase is suspended, and the majority of the o2 that is the by-product of it is reduced, however, the release of O2 is not stopped entirely, and some is still produced as a by product of the dark phase, but not in the same quantity as in the light. i would then think that one would want more circulation (not necessairily circulation as surface agitation), or at least to keep the circulation/agitation that is occurring during the day continued after the lights go out to keep a continuous stream of dissolved oxygen in the water. just a thought. this is also where the concept of the refugium comes into effect. a fuge that is lit 24/7 will be experienceing both light and dark phases of photosynthesis all the time, therefore, major swings in pH from day to night should be practically eliminated, as is the case in my 135 that is filtered solely by a fuge that is lit 24/7. the plants are working overtime, and are continually producing oxygen while both the light and dark phases are occuring and at the same time are producing enough ATP and stored sugars to continue to grow, and therefore continue to filter our water. whew!
now broomer is off on another rant! (j/K brian)
broomer, you mentioned wavemakers and pumps being on timers??? is this the case in your tanks? i personally leave my pumps,wavemakers,returns on all night. this is the first ive ever heard about anyone having them off at night for their fish to rest.
good luck all!
Good stuff everyone I don't think enough reefers pay enough attention to these types of things. We look at whether everything looks healthy and whether tests are ok but never consider the big picture. understanding the big picture is key to success in anything. A good mechanic can fix your car because he understands how it works and what the potential causes of the problem are by going through the processes of the engine etc. A bad mechanic just changes parts until it works. Let's not be bad mechanics and just dump manufactured additives into our tanks without understanding why we are doing it and where we are going with it.
Thanks again everyone for the great info. I'll bet some of this stuff would confuse people at Mensa meetings.
My question is what happens in nature? Are there localized swings in pH caused by night/day cycle or does the influx and efflux of water even out the pH. If in nature there are pH swings (which I don't know what you consider a swing, I am assuming around .2) then why are trying to avoid them. How do we know that pH swings are not part of fish and corals circadiam rythym.
Also, the idea of wavemakers and shuting off PHs during night brings up another good question. What are the currents like during the night. Should the direction of waterflow in our tanks be reverse say by turning one PH off and another on the other side of the tank on? Does it even matter that much?
It is amazing how much we strive to make the creatures we keep feel at home..........
Oh by the way.......I have to come to the conclusioun, Broomer, after being here for a while and reading a lot of your posts lately that you are like Socrates. You answer questions by posing new questions and making people think....in fact that is the best way for a person to learn rather then just regurgitating some data that they will probably forget.
I deem Broomer5 our resident Philosopher!
The alkalinity of natural seawater is around 2.0-2.5 meq/l. To convert to KH, multiply this number by 2.8, to yield about 6-7 dKH. It is generally recommended that a marine aquarium be maintained at an alkalinity somewhat higher than that of natural seawater, between 7 and 10 dKH. The higher alkalinity offsets the accumulation of acids typical of a closed system aquarium. These acids come from several sources, the primary ones being: 1) carbon dioxide from respiration, 2) nitric acid from biological filtration, and 3) organic acids from metabolic wastes.
pH. The degree to which a solution is acid or alkaline is the pH of the solution. Pure water, the standard reference point for many chemical measurements, has a pH of 7, and is said to be "neutral." A solution with a pH less than 7 has more hydrogen ions than pure water, and is said to be "acidic," while a solution with fewer hydrogen ions than pure water has a pH greater than 7, and is said to be "alkaline" or "basic." Hydrogen ions are among the most important chemical species, involved in all kinds of reactions that take place in aquarium waters.
Ions are charged molecules. Hydrogen ions carry a positive charge, as signified by the chemical shorthand for this ion, "H+." Ions can exist only as pairs, with each positively charged ion matched by a corresponding negatively charged one, so that the overall charge always remains at zero. In pure water, the hydrogen ions are balanced by hydroxyl ions (OH-). Just as adding hydrogen ions to the water causes the pH to decrease, adding hydroxyl ions has the opposite effect, making the solution more basic. Adding acid to a basic solution, or vice versa, results in some of the ions recombining to form pure water. This is called a "neutralization reaction."
Alkalinity. The degree to which a solution maintains its pH when acid is added is the alkalinity of the solution. Related terms used in reference to aquariums, are "carbonate hardness," and its German equivalent, "KH." In practice, these terms are used interchangeably, but in reality total alkalinity in seawater is slightly higher than carbonate hardness. This is because the latter is a measure of only the contribution of carbonate (CO3-2) and bicarbonate (HCO3-) to total alkalinity. Various other negatively charged ions, such as borate (BO33-) and hydroxides (OH-) contribute to the total.
Alkalinity is measured in milliequivalents per liter (meq/l). To understand the derivation of this term, and to better understand the concept of alkalinity, it is important to consider the neutralization reaction. The general formula for a neutralization reaction is written as follows: H+ + OH- ---> H2O
Note that identical amounts, equivalent amounts, of both hydrogen and hydroxide ions are involved. Different chemical compounds will yield up different amounts of ions when dissolved in water.
Chemists long ago recognized the need for a standard way of making solutions from compounds. We would like to know exactly how many individual ions there might be in a solution. To do this, we first total up the molecular weight of the compound in question. In the case of water, there are two atoms of hydrogen, atomic weight 1, plus one atom of oxygen, atomic weight 16, so a gram-molecular-weight, or mole, of water is 18 grams. One mole of anything contains exactly the same number of individual particles, whether atoms, molecules or ions. If we dissolve one mole of nitric acid in 1 liter of water, we get one mole of hydrogen ions (H+) and one mole of nitrate ions (NO3-) in the solution. We create a standard solution, called a molar solution, abbreviated as 1 M. This is a solution of acid; it contains one mole of hydrogen ions, and chemists call such a solution a normal solution (1 N). A 1N solution delivers one equivalent of either acid or base, in any volume. The combining ratio of such a solution is a constant.
Returning to the measurement of alkalinity, we are determining how many equivalents of acid must be added in order to combine completely with the bicarbonate, carbonate, borate, hydroxide and other ions present in a seawater sample, without adding an excess of hydrogen ions. We do this by performing a titration, adding a normal acid solution drop by drop, and noting when the endpoint is reached. The endpoint of the total alkalinity titration is reached at a pH of 4.5. Determination of the endpoint can be done precisely using a pH meter. If one does this, noting what happens to the solution's pH with the addition of each drop of acid, one obtains a graph that looks like the one shown below.
By inspection of this graph, we can see that the pH remains stable for the first few additions of acid, and then drops precipitously as the endpoint is approached. The initial stability of the pH reflects the fact that the seawater is a buffer. Buffers are solutions that resist pH changes. This is why you will sometimes hear alkalinity or KH referred to as "buffering capacity."
I don't know for sure about the stabiltiy of the oceans pH - but I imagine it's a lot more stable than that of our tankwater.
At least generally.
Maybe in some very shallow lagoons, or areas of high algae concetration - the pH swings somewhat.
I don't know.
The " let's give the fish a rest " at night by turning off powerheads or reducing water circulation - I mentioned that because I see it here often.
I don't know if fish care about this or not. I have a feeling that it's more of a human feeling the need for calm waters, rather than a requirement for the fish to be comfortable at rest.
Especially if you have a lot of live rock, or hiding/resting places for the fish. Maybe in an open FO tank this would considered wise.
My point was just that water circulation and gas exchange, specifically CO2 concentrations in the tankwater - will have an impact on the swings in pH.
The largest effects being if you have a tank with a lot of fish and algae growth - changing the water circulation pattern or duration the powerheads are on - MAY contribute to the swings.
Then again - it may not. Depends entirely on each tank's set-up and inhabitants.
I'll take that as a complement.
How about a variation on Descartes - I think .. therefore I am,
I reef .. therefore I struggle with water conditions
Lastly to falcon63 ...
I'm sorry you feel that some of the sharks "spat off" when asking questions or replying to threads.
Some questions and topics are easy to answer with short to the point replys - while other's may require more text to explore the possible cause for a members concerns.
Some want to know "how to correct"
Some want to know "how to correct and prevent"
Some want to know "how to correct and prevent and why does this happen"
Most of the mods, as well as many of the members here subscribe to the last scenerio.
Not just how to fix a problem, but how to keep it from happening again - and WHY did it happen in the rfirst place.
My simple short answer to this thread would be much easier for me if all I said was.
"Don't let your water parameters get whacked out, and if you do, fix it"
hmmmmm well in my opinion (admittedly worth very little) when I pose a question to the forum I appreciate the "why" of the answer as much as the answer itself. I enjoy broomer's "rants", haven't read one yet that didn't *learn* me something. I agree, there are some posts that only warrant a simple yes/no answer, some, such as this, present an opportunity to learn more about the "why's" of our hobby.
Just my .02,
Originally posted by falcon63
make it stop
Awww c'mon Falcon, you're degrading a perfectly good thread.
Broomer wasn't even answering a question, he was putting out some very valuable information and starting a "thinking" person dialog aka debate. I found it refreshingly informative and very useful.
Broomer....I confess it was me that stuck this jewel up top...and I really think it should stay a while.....very informational. Best example of all the positives of this board....also a great example of the experience/knowledge of our active members. Outstanding thread folks....now excuse me while I re-read all the above info....only after taking several small
to relieve the massive headache all that info created the first time I read thru.......and to think this all started over a "Broomer" rant.......