Man oh man did we ever get off topic. Ok well this has gotten long and quite boring but here goes. ¡§> I'm afraid that it is you that has confused a few > issues. Let's see if we > can walk through this in an academic manner and > arrive at some sort of ?« "consensus", shall we?¡¨ Indeed we shall however you used allot of words David yet you failed to really say anything relevant to the topic here. Perhaps I shall explain this relationship in ¡§plain ¡§ English so the rest of the group can understand. I think for the purposes of this audience we should proceed in a more practical matter. Please explain how this affects our aquariums and fish keeping and the"Topic" how we do or do not need CO2 in our aquariums. The pH of a natural body of water is in large part determined by the chemistry of carbon dioxide. Dawes, C..J. 1981 Aquatic Botony. CO2 is a very soluble gas which is normally found at concentrations of 45-55 ml/l in natural bodies of water far less the is found in the air we breath. CO2 enters the water system via land run off, through the surface from the atmosphere and is released by aquatic plants and animals during respiration. In addition the action of bacteria breaking down waste products will also release free CO2 as they metabolize fecal matter and dead tissue. ¡§the CO2 > concentration as essentially ?« fixed¡¨ That is very wrong and your mistaken David Y. I don¡¦t know about your tanks but there is feces and loads of bio activity that will release CO2 in to my system not to mention fish respiration. This goes to my argument about water changes as we allow the water to accumulate DOC¡¦s, nitrates and other inorganic compounds the pH will go down. Let me explain this further. Most of the CO2 combines with water (remember hydration from Bio 101) and forms a weak acid-carbonic acid. Less the 1% of the CO2 present in a body of water is in the form of ambient CO2. The carbonic acid then dissociates into carbonate bicarbonate ions. These compounds are in equilibrium with each other. That is to say that the chemical reactions shift back and forth with the changing conditions and retain the same ratio or chemical balance. This is the pH equation I was talking about David Y. ¡§There is no "pH equation", per se - only the > _definition_ of pH, which is an > inverse log of the actual *count* of hydrogen ions > in a solution. It's a log > scale because we're dealing with _huge_ numbers > here, and the numbers we ?« _do_ use are in effect the *exponent* of the value¡¨ ¡§Did you catch that "fixed" part? That means it > doesn't change. Therefore, > the only thing really influencing the final pH is > the bicarbonate > concentration.¡¨ ¡§The rapid increase or decrease of CO2 has the greatest immediate effect on the pH of a natural body of water. Removal of CO2 lowers the amount of carbonic acid and pH increases. Addition of CO2 increases the amount of carbonic acid and pH decreases¡¨ Bardach, J.E., J.H. Ryther and W.O. McLarney. Aquaculture This is why we don¡¦t need a CO2 injection system if we have enough free CO2 in our system through a low KH and low pH there will be plenty of carbonic acid present , this we get from the chart. Not to mention the metabolic functions of fish and waste decay. ¡§It is _not_ the incorrect way of looking at this - > it _is_ the *only* way to > look at this. The "KH" is THE primary natural buffer > within the equation. So > if you have no buffering agent, you can have no ?« > buffering. ¡§ I don¡¦t know where you are going with this but I will stick to what I have said. It seems you have used allot of big words david but you have failed to explain anything in any practical sense. I don¡¦t really care about chemistry other then how it relates to my fish keeping and breeding. Here is the bottom line in plain English no fancy words needed. A low KH will help keep a low pH. A high KH will have a tendency to a high pH. If you are having trouble maintaing a low pH say, 5.5 or even 4.5 then you will need a KH of 0 to get there. Simple no fancy words needed and everyone understood. ¡§There _are_ other > buffers at work in our Apisto tanks down at the > ranges we work on, and their > related to the humics most of us introduce through ?« peat/tannin filtering¡¨ Thanks for confirming what I just said. ¡§But be forewarned - my reading includes people like > Arrhenius, Bronsted, > Lewis, Dalton, Henry, LeChatlier, Boyle, Charles and > their ilk. And my > practical experience is approaching the fourth ?« decade...¡¨ Ok? I don¡¦t know what to think of that¡K.. Anyway I can appreciate your knowledge of Chemistry David Y. Obviously you have a love for this stuff. However you have failed in my opinion to explain anything only say allot of big words about pH. For the purpose of this forum I would suggest you take it slower and put the knowledge into practical terms. I don¡¦t really care to hear about pH mombo jumbo I want to know how it effects my tanks and my breeding. I also think you need to explain things in terms that would be more relevant to this audience. I am far from an expert on Chemistry. But be forewarned ?º I do know what works in the aquarium and why from my 2 decades of experience of putting them into practice. You're a Floridian - ever go looking for Elosoma (dwarf sunfish)? Particularly Elosoma evergladei? They frequent soft, acidic springs with little DOCs and an excellent source of carbon - the gas that bubbles up in the spring. Check out the types of plants that grow in those headwaters. Actually your very incorrect these fish are found in water with a pH of 7.8-8.2 and a KH of 15 and 21 DH, in Florida anyway. And I have not seen any of the things you talk about. Ellassoma sp. that I have found have always been in hard alkaline water. If you understood Florida you would know why an acidic soft water spring is impossible. We have the aquifer. It is liquid rock. Perhaps the CO2 bubbling is correct but do lakes have that? Ponds? Other rivers? BIG NO! Also since the water is from the aquifer, no aeration kinda like a well, hint, hint you guessed it lots of CO2. And now that we are finally back on track to the topic of discussion. Since you are so versed in water Chemistry perhaps you could explain why CO2 is needed in an aquarium? I will stick to my argument regarding free CO2 in a system of water. You have said many words David Y yet you have not explained this. Which is after all our topic of discussion. A CO2 injection system is not needed when there is already enough CO2 in an aquarium with LOW KH and pH. If you disagree please explain why you do so. Hopefully in a manner that we can all understand and relate to. Mind you I fully understand all you have said though I find such information rather mundane. Perhaps you could show a deep understanding of your knowledge through applying it to our topic of discussion mainly why we do or do not need a CO2 injection in an aquarium. Keep well. I hope you get better from your cold. David Sanchez __________________________________________________ Do You Yahoo!? Great stuff seeking new owners in Yahoo! Auctions! http://auctions.yahoo.com ------------------------------------------------------------------------- This is the apistogramma mailing list, firstname.lastname@example.org. For instructions on how to subscribe or unsubscribe or get help, email email@example.com.