Buffering RO/DI?

[Anthony Calfo]

cheers, Wy

With the caveat here that we must always test our water (trust but verify) to be sure things are going as we hope and planned, the answers to your questions are as follows:

- yes, it is very possible to get away with little or even no buffer supplements when dosing calcium hydroxide faithfully (that would be at night, most certainly)

- if you are topping off with completely demineralized water...then, well ya gotta buffer at some point. Using a good liquid 2 or 3 part supplement faithfully in the display (as consistent as you dose evap to an extent here) then you can get away without reconstituting the RO/DI water. The concern however is for abuse or neglect. Adding raw, sour, acidic water to the system daily without buffering daily can be a problem fast. But habitually buffering raw water before it ever gets used is a more conservative and safer strategy IMO. So yes, I am recommending all RO or DI water get reconstituted mildly to be less of a burden to sea salt or the system as evap water

- I dont have strong brand preferences. There are many good ones out there. I've used Brightwell, TLF, Seachem. Really...any decent brand uses quality reagents. The onus is on you to reckon how complex you want or need them to be. A system with large water changes (heavy fishload, farming tanks, etc) can get away with the classic tribuffer recipe (Aquarium Systems "Seabuffer"). But hobbyists that dont want to do as many water changes or even reconstitute RO/DI water may want, I think as Rick suggested, to just does the system. Thats a circumstance for a good 2 or 3 part (liquid) supplement.

- as for any sea salt brand that claims their product mixes fine with demineralized or tap water, I call bull. Sure, they can squirm out of the wording. They say "purified" which you and I may believe means demineralized (RO/DI) but they escape with "carbon filtered tap water" yeah...its purified. Also, and I empathize with them...they are pitching to consumers using "tap water" but tap water in Guam, Seattle, Desert cities and NY do not have even remotely similar tap water. So its a challenge to mix and market a safe and successful recipe. Ultimately, its the consumers responsibility to test and understand their water and use of a given product. If you have insanely hard tap water and you make the likely mistake of using an enriched sea salt...problem. Or...if you use an economy sea salt (weak alk, etc) with untreated raw acidic pure RO water...also a problem.

Bottom line is that you have to test and finesse for your specific situation.

 

[Reef UP]

I add Kalk to my top off container it's a typical rubbermade trash can I fill it to the 20g mark I add 10tbls to it and it gets mixed every night 3 hours and stops one hour before my lights turn on.
I use to run my ph like the rest of the common reefers it had a swing of 7.8-8.3 now it stays in the 8.4-8.6 range and wow oh wow the difference in the appearance of my sps my acros are all super hairy and the tissue appears to be super healthy they put off a super slime when handled and have been healing faster when fragged! Anyone think this has something to do with the stable higher ph? My other params are
Alk 7.5
Cal 420-440
Mag 1550
Nitrate 0
Po4 0

 

[drainbamage]

I'm replying to your first post in this thread (errr...not very first, but the first explanatory one)

In this, you write that the reason to buffer RO/DI for top off is for PH control, and how everything in a tank is working against PH stability- could you elaborate on why PH, and a certain value of it, is so essential?

Also, you reference that mineral stability is key-but you recommend adding minerals to the top-off water. Unless I'm missing something, isn't top-off water meant to be mineral deprived to ensure you aren't adding excessive minerals? That's at least always been my approach, considering your example of a sump with a given alk of 10dkh (representing an abundance of minerals to a certain degree) being negatively affected by the evaporation top-up water. However, doesn't this fail to take into account the excess minerals in the original water, excess owing to the set baseline with initial water volume, reducing water volume by evaporation while the minerals remain?

Lastly, in regards to the acidic slide-in a tank that is dealing with organic wastes through exportation methods (bacteria boosting via carbon source, removal via foam fractioning, natural processes (algae filters,) and reduction methods via water changes) would an acidic slide be actually occuring because of waste? Depletion of minerals (and relative water hardness movement) is primarily caused in my tanks by uptake by the organisms in the tank- if my mineral levels deplete to a certain point, corals stop growing, but mineral levels do not deplete beyond that point any further until I return the balance of minerals, meanwhile the organic introductions into the tank are unchanging (fish are still pooping, food is still being fed.)

Thanks for the discussion!

 

[Anthony Calfo]

cheers, Drain

In regards to your first quest, an excellent one and one that I don't hear as often. Folks are excessively fixated on Calcium levels and ignore ALK. Or, they pay attention to alk but not Mag. All of which must be reckoned to begin with for satisfying calcification, and none of which will happen optimally if there are wild pH swings. In closed aquarium systems we just don't have the expanse and stability of the ocean to take soft or acidic rain or run off (read: evap water). The ratio is a dwarfing scale of magnitude in our tank with evap added on a daily (or worse if less often) basis to our little slice of seawater. So at face value - salinity fluctuations and stress from it aside - we (reef hobbyists) have a challenge to reckon with in adding soft unstable freshwater water to a rather small volume of seawater.

While the big picture here is maintaining stable and adequate mineral levels, the truth is that you can easily get great coral growth with calcium levels at 300ppm, or 375 ppm, or 425ppm. Your system really won't "care" (read: show a response or stress) so long as the same X ppm (10 or 20 or whatever your system draws) is available. In fact, you could do a water change and raise your calcium (in balance with other components) from 300ppm to 400ppm and really not phase most if not all inhabitants in the tank. You can NOT do that with pH. A similar 25% change up or down in pH will frankly destroy the system.

Reef creatures are very sensitive to slight changes in pH. It affects a plethora of functions. Very experienced fresh and saltwater aquarium keepers alike can actually tell the trends in ph of a given aquarium by the waxing and waning of notable lower order algae varieties in the system (a sliding scale of algal succession). In short, reef organisms are very sensitive to changes in pH and a sable pH is indicative of the health of other necessary params, such as alkalinity (mineral hardness/buffering ability of water).

We can raise or lower the "temporary pH" (scientific definition) with baking soda or phosphoric acid respectively, for example. But the alkalinity of the system for a while will bring that back to center. By remineralizing our evaporation top off water, we are insuring that this unstable pure water does not burden but rather helps the buffer pool in our reef tank which is constantly losing alkalinity from calcification, organic acids and other natural processes (the so-called acidic slide).

Getting back to your specific questions, I respectfully suggest that you have a bunch of misperceptions in the following statement:
----
"Unless I'm missing something, isn't top-off water meant to be mineral deprived to ensure you aren't adding excessive minerals? That's at least always been my approach, considering your example of a sump with a given alk of 10dkh (representing an abundance of minerals to a certain degree) being negatively affected by the evaporation top-up water. However, doesn't this fail to take into account the excess minerals in the original water, excess owing to the set baseline with initial water volume, reducing water volume by evaporation while the minerals remain?"
----
No...as per my points in the thread so far, the top off water is not intended to be mineral deprived IMO. And for others, again citing Ricks alternate approach, you still must reckon the deficiency in the system with perhaps liquid buffering supplements. I do care how you do it (previous post suggesting mineralizing all incoming water is safer than admitting raw unsable water and counting on faithful dosing to counter it)...but ultimately it doesn't matter how you do it as long as you get it done. Perhaps you and Rick are the sort of folks for whom very consistent dosing is no trouble at all. the reality is that most aquarists cannot be that extremely consistent and do not test their water quality and dose accordingly over time.

You also wonder if the acidic slideis primarily from organic waste. No...the reality is that folks have all sorts of other influences, CO2 buildup in the water from well insulated homes (winter and summer especially when less windows are open), CO2 from Calcium reactors, carbonic acid in RO or DI water, etc.

You also state that you believe the "depletion of minerals (and relative water hardness movement) is primarily caused in my tanks by uptake by the organisms in the tank" and that is also not a common reality for so many folks on the calcium and alk supplementation seesaw. Without fully understanding their water chemistry, they may shovel in loads of one or the other over time and still be frustrated that their tests are reaching their targets. That begs the question, where is all that mineral supplementation going? Precipitation. And not always (rarely in fact) does that occur in the tank like the dreaded "snowstorm."

Lastly, it sounds like you are frankly a better than average aquarist. I say this because the nature of your curiosity seems to be from a lack of experience (God bless you for it) with the common problems that most folks have dosing supplements and maintaining desired alk levels. Case in point, your "[presumed alk of 10dKH]" is higher than the average reefer, by far, IMO (considering the folks that aren't forum savvy, but instead are depending on knowledge on the high school kid selling them fish at their local pet shop). 8 to 12 dKH is my preferred range, and a majority of folks I talk to dont even see 9 on that scale consistently.

And lastly, at the risk of opening up a can of worms with a mostly anecdotal observation (LOL), I have observed in my 20+ years of growing corals that I get faster and more consistent calcification/growth in my creatures when my alk is faithfully high (think 11-13 dKH) and my calcium is "normal' (under 425ppm...often much lower). I believe that the obsession with obscenely high calcium in recent years has allowed a greater message of broad mineral level strength (indicated indirectly by high and steady pH and ALK) to be unfortunately lost. Of the dozens upon dozens of private reef tanks I visit every year, I'm amazed at how many people have or use a calcium test kit, but do not have or use their alkalinity test kit. Just an example.

 

[VegasRick]

Well Anthony, lets do keep this friendly shall we? The link is broken, which is too bad as it was a great collection of pH readings from a half dozen or more reefs. As for qualifying "what I have seen" I was referring to those pH readings on that link and other research papers. With all the controversy over the acidification of oceans there should be many more available, however now they tend to look at long term instead of daily fluctuations. But since you have first hand data perhaps you'd like to share it. You said you were being paid to collect them? So you should have a good log of days times locations and methodology. I am curious on what daily fluctuations you have seen.

I thought maybe AZDesertRat would have responded back since he has a great deal of knowledge on RO systems, but since he never did I will. I think my understanding was similar to his on the ph of ro water. So when you dismissed his comments I did a little research to find the basis for the ideas we seem to have on it. Here is a copy and paste from the Water Quality Association that explains it in simple enough terms that I can understand

.....Water that has been produced by a properly functioning reverse osmosis system is some of the purest water available, yet often RO users are surprised and a little alarmed to find that their very clean water is also “acidic”, that is, that it has a low pH. Neutral pH is defined as 7.00, but RO water typically shows a pH of between 5.00 and 6.00.
.....Given that the pH scale, like the Richter scale for earthquakes, is logarithmic, that means that pH 5.00 water is actually 100 times as acidic as pH 7.00 water. Certainly, that sounds very drastic, but due to the somewhat unique properties of RO water, there really is no cause for alarm.
.....First, it may be helpful to look at what pH measures. pH is a measurement of the relative acidity or alkalinity of a solution. Some substances, such as hydrogen ions, lower the pH of a solution. They are considered acids. Other substances, such as hydroxide ions, raise the pH of a solution. Those are called bases.
.....There are many different acids and bases that affect pH, but for clarity sake it will be easiest to think only in terms of hydrogen ions (H+) and hydroxide ions (OH-). When water has more free hydrogen ions floating around than hydroxide ions, it is acidic (pH less than 7). When there are more hydroxide ions than hydrogen ions, it is basic (pH greater than 7).
.....Water, as we have all learned, is described by the chemical formula H2O. If you could shrink down small enough to be able to see molecules, when you looked at a glass of water, you would see that the water molecules did not simply stay put as H2O, but were always separating and recombining. An H2O would break in to two pieces: an H+ and an OH-, and then get back together. In that glass of water there would be gazillions of water molecules, all splitting and rejoining constantly. If that water were very pure RO water and didn’t have any other substances dissolved in it, the pH would be neutral.
.....Because there are only H2O molecules there, the number of H’s and OH’s would be even. There wouldn’t be more H’s than OH’s, or the other way around, and so the acidity of an H+ would be “cancelled out” by the alkalinity of an OH-. This balance between hydrogen ions and hydroxide ions is what makes a solution neutral. Therefore, extremely pure water is always neutral because it doesn’t contain any other substances to throw off that H/OH balance.
.....Why then does RO water test to have a low pH? The very purity that means it is neutral also makes it very sensitive to the addition of other substances. Technically speaking, RO water has little or no buffering capacity. That means that the addition of even a small amount of acid will have a large effect on pH.
Regular, untreated tap water typically contains chemicals that act as “buffers”. When some H+ is added to typical tap water, some of those buffers “catch” the H+ and combine with it. Then, even though H+ has been added, the pH doesn’t change because the amount of free H+ floating around is still the same relative to the amount of free OH-. Because a reverse osmosis removes the vast majority of those buffer chemicals, when a little bit of H+ is added, it upsets the balance between free H+ and free OH-.
.....Reverse osmosis membranes do not remove gasses, such as carbon dioxide in water. Also, when RO water is exposed to the air, a small amount of carbon dioxide will begin to dissolve in the water. So RO product water has the buffering alkalinity chemicals removed and the acid causing gasses remaining.
.....Again, if you were small enough to see molecules, what you would see happening is this: You would see the carbon dioxide molecules combine with some of the OH-‘s in the water. That means that there would be relatively more free H+’s floating around, because some OH-‘s had been “caught” by the carbon dioxide in the water. Having more free H+’s than OH-‘s floating about is how we earlier defined an acidic solution, so that is why the pH of RO water is typically lower than neutral.
.....Having low pH RO water should not be of concern because the “acidity” in RO water is very weak. In order to bring RO water to a neutral pH, it takes only a tiny amount of base. For example, if you had a glass of RO water with a pH of 5.0 and you added 2-3 specks of baking soda (a base) that would likely neutralize the tiny amount of acidity in the water.
.....For someone who is concerned about the effect of low pH RO water on the body, I would not recommend going through the trouble to add specks of baking soda to every glass of drinking water. The moment a person drinks some low pH RO water, that water will combine with the saliva, and, moments later, the stomach contents. It will cease to be extremely pure (because it will have saliva and chewed up food in it), and so it will no longer have the unique pH characteristics described above. Additionally, the pH in the stomach of a healthy person is typically less than 2. That is very, very acidic. As soon as the water gets to the stomach, it will become very acidic, also.
.....That acidity is essential to human health. Without the acid in our stomach, we would not be able to digest our food, and we would get sick much, much more often because stomach acid kills many bacteria and other things that we ingest. The only way that drinking low pH RO water could upset the pH balance of the body might be if someone drank ridiculously large amounts, and didn’t eat anything, and continued that for some time. Barring that situation, drinking low pH RO water will have basically no effect on the pH of the body.

So that sounds to me that the ro water is neutral. CO2 in the water itself would be removed then by the DI resins and exhaust those resins quickly if excess was present. The co2 in our homes though would have an affect although probably minimal. I don't see ro water as much of a contributor to the decline of pH in our tanks.

I also keep my alk 10+ and seem to have the best results. The trend these days to keep lower alk seems to come from those people dosing vodka or some type of carbon source and the reports they have given of higher alk causing problems with sps. To compound it they then make recommendations to those not using a carbon source on what to keep their parameters. So then you end up with mixed methodology.

 

[Monroereef]

I have never done it. I think the parameters depend a lot on the kind of salt you use.

 

[Wy Renegade]

So that sounds to me that the ro water is neutral. CO2 in the water itself would be removed then by the DI resins and exhaust those resins quickly if excess was present. The co2 in our homes though would have an affect although probably minimal. I don't see ro water as much of a contributor to the decline of pH in our tanks.

I also keep my alk 10+ and seem to have the best results. The trend these days to keep lower alk seems to come from those people dosing vodka or some type of carbon source and the reports they have given of higher alk causing problems with sps. To compound it they then make recommendations to those not using a carbon source on what to keep their parameters. So then you end up with mixed methodology.

Rick, just a couple comments/thoughts I have. I'm very confused by your assertation that RO/DI is neutral - the article clearly states that RO/DI water is in fact 100 times more acidic than tap water, then goes on to confusing asertain that it truth its a weak acid. Followed by statements that pure whater should have a pH of 7, but RO water, which is supposed to be pure has a low (acidic pH). I'm glad you understand it, cause as a biologist, I personally find it to be a very confusing article of counter intuitive points.

Secondly on the request for detailed scientific data - seriously?! Why is it that every time one of the discussions comes up on the boards, everybody who participates, who isn't a scientist wants to go hide behind detailed scientific data (sorry if thats a bit of a rant, but it is one of my pet peeves). Somebody makes an observation and somebody else says, where is the scientific data to back that up? 90% of what is stated in this hobby as based on fact and science, is based on nothing more than people observations and conclusions drawn from those observations, not actual data. And just to be clear, that is also good science. 99% of the people on these boards would be completely overwhelmed and boarded to death with the actually presentation of true scientific data. Just my $.02 worth. Rick you're basing your observations and conclusions on analletical data you've read that somebody else has reported - that admittadly you don't have a link to anymore. You're really gonna call on somebody else who has actually collected the data to present dated detailed lists rather than simply taking his word for an overall conclusion he's drawn based on that data? Again, sorry if this seems like a bit of a dramatic rant, but as I stated, its one of my pet peeves .

 

[VegasRick]

Rick, just a couple comments/thoughts I have. I'm very confused by your assertation that RO/DI is neutral - the article clearly states that RO/DI water is in fact 100 times more acidic than tap water, then goes on to confusing asertain that it truth its a weak acid. Followed by statements that pure whater should have a pH of 7, but RO water, which is supposed to be pure has a low (acidic pH). I'm glad you understand it, cause as a biologist, I personally find it to be a very confusing article of counter intuitive points.

Well my understanding is, and I could be wrong
RO/DI water is in fact 100 times more acidic than tap water...because tap water has alk, then even at a neutral pH of 7 ro water is more acidic than tap water, the 100 times is just the nature of the ph scale
but RO water, which is supposed to be pure has a low (acidic pH)....caused by co2 in the water, ro membranes don't remove it, but DI resins will
that still leaves exposure to co2 in the room where its stored

As for the request for data, I am more interested in the daily swings, I thought I remembered pretty large swings in some places, but since its no longer available I can't really use it anymore. And since we have a man here that has the raw data what better to look at.

 

[mdb_talon]

Well Anthony, lets do keep this friendly shall we? The link is broken, which is too bad as it was a great collection of pH readings from a half dozen or more reefs. As for qualifying "what I have seen" I was referring to those pH readings on that link and other research papers. With all the controversy over the acidification of oceans there should be many more available, however now they tend to look at long term instead of daily fluctuations. But since you have first hand data perhaps you'd like to share it. You said you were being paid to collect them? So you should have a good log of days times locations and methodology. I am curious on what daily fluctuations you have seen.

I thought maybe AZDesertRat would have responded back since he has a great deal of knowledge on RO systems, but since he never did I will. I think my understanding was similar to his on the ph of ro water. So when you dismissed his comments I did a little research to find the basis for the ideas we seem to have on it. Here is a copy and paste from the Water Quality Association that explains it in simple enough terms that I can understand


So that sounds to me that the ro water is neutral. CO2 in the water itself would be removed then by the DI resins and exhaust those resins quickly if excess was present. The co2 in our homes though would have an affect although probably minimal. I don't see ro water as much of a contributor to the decline of pH in our tanks.

I also keep my alk 10+ and seem to have the best results. The trend these days to keep lower alk seems to come from those people dosing vodka or some type of carbon source and the reports they have given of higher alk causing problems with sps. To compound it they then make recommendations to those not using a carbon source on what to keep their parameters. So then you end up with mixed methodology.

Vegas,

I find it interesting you would mention the acidification of the ocean. This itself should tell you that even minor changes in PH can have significant issues to coral health, and intuitively that low PH is a bad thing.... All your bulletpoints you pasted are useless to me personally. The article you pasted was clearly about the affect of humans drinking low ph water. It is not the same thing as shocking your corals by repeatedly adding acidic water to their habitat. I can eat 6 twinkies a day and at least short term the only affects are a slight increase in belt size. Put 6 twinkies a day in your tank and I doubt the results for your coral would be good. I guess my point is the information Anthony Calfo is giving us is specific to a situation and it is useless to bring in research from something unrelated. Needs, requirements, and what is "safe" or ideal is not the same for corals and humans.

I am not sure I completely understand this, but the way I understand it I dont see how you dont think adding unbuffered water can have any longterm affects on PH. If you continually add unbuffered water to an aquarium the water will have less buffers eventually (with assumption that the buffers in there are being used up by living organisms or precipitated out). If nothing else the water that is not sufficiently buffered is going to have wider PH swings, and the way I understand it over time will have a lower PH. You could buffer directly to your tank, but that does not negate the shock of adding the unbuffered water with a different PH, sure the water is volatile and will quickly change PH because it was unbuffered. Now you have to some extent created more volatility in your whole tank though as I understand it.

As for Anthony Calfo showing us his logs/research/methodology. Honestly I just think that is silly. If I claimed to have sampled ocean waters in reefs all around the world then a request for proof/methodology or a healthy skepticism is completely warranted. Requesting the same of someone like Anthony Calfo makes you appear to be childish and just not capable of admitting when wrong. I would also assume there are more practical reasons why he would not or could not show us research data. As he clearly said in his post he was paid to do this research in which case it is very possible the data is not his to share anyway. I have no problem taking him at as word when he shares his experience with us, he is not writing a research paper here he is kindly sharing his well respected knowledge an experience. Lets challenge him on things if we think it valid maybe everyone can learn something, but lets not be so petty as to question objective facts he is telling us that are very specific to the situation. If he says he has surveyed the applicable parts of these reefs all over the world and the PH is generally not 7.8 to 8.2, but is usually 8.4 or higher then that is good enough for me.

 

[drainbamage]

Uhm....my questions didn't get answered with the details I was looking for, just the same generalized statements, so hopefully can maybe get some more detailed answer?

Oh, and most folks consider RO/DI water "neutral" based on the PH scale. 7.0 (which typical RO/DI should read) is neutral PH, higher than that is "hard" and lower is "acidic." Thus RO/DI will be more acidic than many folks tapwater (considering most have aquaduct systems providing water as opposed to a well system,) but that doesn't make it "acidic" in the same fashion as distilled water is.

 

[beaslbob]

Uhm....my questions didn't get answered with any details, just the same generalized statements, so I guess I'm not going to be able to get any useful info out of this thread, bummer

Oh, and most folks consider RO/DI water "neutral" based on the PH scale. 7.0 (which typical RO/DI should read) is neutral PH, higher than that is "hard" and lower is "acidic." Thus RO/DI will be more acidic than many folks tapwater (considering most have aquaduct systems providing water as opposed to a well system,) but that doesn't make it "acidic" in the same fashion as distilled water is.

sorry.

I would not buffer the ro/di and then make adjustments as necessary to the tank.

But that's just my approach.

Worth at most .02

 

[Wy Renegade]

Well my understanding is, and I could be wrong
RO/DI water is in fact 100 times more acidic than tap water...because tap water has alk, then even at a neutral pH of 7 ro water is more acidic than tap water, the 100 times is just the nature of the ph scale
but RO water, which is supposed to be pure has a low (acidic pH)....caused by co2 in the water, ro membranes don't remove it, but DI resins will
that still leaves exposure to co2 in the room where its stored.

Hhhmmm not sure I agree with your thought process. According to the article, RO water is testing at a pH of 5 or 6, not pH 7. That resulting pH is according to the article, as you point out, a result of the CO2 gas reacting with hydroxyl ions and bonding to them, resulting in a increase in free hyrogen ions, hence an acid. However, an acid is an acid is an acid. While 5 is a relatively weak acid (just as an example, household vinegar has a pH of around 5), and is therefore is relatively easy to revert to neutral, I don't think that most people would argue that pouring a gallon or two of vinegar into your tank on a daily basis isn't going to have an effect on pH.

While the DI resins may remove any CO2 gases from the initial water, continuing to have those CO2 gases remain removed would require that your RO system be completely airtight with absolutely no air exposure, and that the jugs you are pouring into would have to be vaccume treated prior to filling with completly no air exposure during or prior to the water being poured into the tank. If these conditions are not in place, the removal of CO2 gas by DI resin in irrelavent, as new CO2 will be readily absorbed from the air exposure. I don't know about your system, but I guarantee that my RO/DI is not air tight.

As for the request for data, I am more interested in the daily swings, I thought I remembered pretty large swings in some places, but since its no longer available I can't really use it anymore. And since we have a man here that has the raw data what better to look at.

Aaahhh, now see you have a very specific reason for asking, and had the question been asked more to this point, IMO it would have come across in a much more reasonable manner. Again, just my $.02 worth

 

[Wy Renegade]

Uhm....my questions didn't get answered with any details, just the same generalized statements, so I guess I'm not going to be able to get any useful info out of this thread, bummer

Oh, and most folks consider RO/DI water "neutral" based on the PH scale. 7.0 (which typical RO/DI should read) is neutral PH, higher than that is "hard" and lower is "acidic." Thus RO/DI will be more acidic than many folks tapwater (considering most have aquaduct systems providing water as opposed to a well system,) but that doesn't make it "acidic" in the same fashion as distilled water is.

But if you read the article Rick posted, RO water doesn't read with a pH of 7.0, it tests out at Ph 5 or 6. Just for my own curiousity, how is distilled water acidic? I assume it would have to be a similar explaination, but just satisfying my curiosity.

 

[beaslbob]

But if you read the article Rick posted, RO water doesn't read with a pH of 7.0, it tests out at Ph 5 or 6. Just for my own curiousity, how is distilled water acidic? I assume it would have to be a similar explaination, but just satisfying my curiosity.

pH lowers as carbon dioxide increases. I think with RO/di and even just tap water for that matter, the water has been confined places like the plumbing and therefore has more co2.

Simply exposing the water to the air will cause a rise in pH as co2 dissipates.

algeas will further raise the pH to very high levels as the algae sucks out co2.

With lower kh values the ph will drop at night unless lights are on 24 hours like is a refugium with reverse lighting.

But that nightly pH drop will be greatly reduced as kh values are around 8-12 degrees or so.

At least I think.

Which should be worth at the most



.02

 

[drainbamage]

But if you read the article Rick posted, RO water doesn't read with a pH of 7.0, it tests out at Ph 5 or 6. Just for my own curiousity, how is distilled water acidic? I assume it would have to be a similar explaination, but just satisfying my curiosity.

Sorry, I admit I haven't read the entire thread-I read the original post by Anthony, then his response, and got sorta bummed out by the lack of information I was hoping to get out of it.

What I've always understood by research, stripped water (RO) should read around 7, which is "true neutral" (at least in every chemistry class I've ever taken)

can't imbed for some reason, but here's an image worth a glance
http://ga.water.usgs.gov/edu/graphics/phdiagram.gif

When the water is further depleted, it becomes "acidic" -distilled being one of these. By distilling-where only the pure H20 molecules are ideally collected from the steam vapor, there is a reduction of anything that is not H20 in the end solution. Thus the greater acidity of the distilled water.

This site had some good info
What Is the pH of Distilled Water? | eHow.com

and excerpt

Identification
Distilled water ideally consists of only hydrogen and oxygen, with a completely neutral pH of 7. In reality, it almost always is slightly acidic, from 5.6 to just under 7, because the water absorbs carbon dioxide from the air. A gallon of distilled water can be made neutral by adding 1/8 tsp. of baking soda, a substance with a pH of 8.

 

[VegasRick]

I'm replying to your first post in this thread (errr...not very first, but the first explanatory one)

In this, you write that the reason to buffer RO/DI for top off is for PH control, and how everything in a tank is working against PH stability- could you elaborate on why PH, and a certain value of it, is so essential?

Also, you reference that mineral stability is key-but you recommend adding minerals to the top-off water. Unless I'm missing something, isn't top-off water meant to be mineral deprived to ensure you aren't adding excessive minerals? That's at least always been my approach, considering your example of a sump with a given alk of 10dkh (representing an abundance of minerals to a certain degree) being negatively affected by the evaporation top-up water. However, doesn't this fail to take into account the excess minerals in the original water, excess owing to the set baseline with initial water volume, reducing water volume by evaporation while the minerals remain?

Lastly, in regards to the acidic slide-in a tank that is dealing with organic wastes through exportation methods (bacteria boosting via carbon source, removal via foam fractioning, natural processes (algae filters,) and reduction methods via water changes) would an acidic slide be actually occuring because of waste? Depletion of minerals (and relative water hardness movement) is primarily caused in my tanks by uptake by the organisms in the tank- if my mineral levels deplete to a certain point, corals stop growing, but mineral levels do not deplete beyond that point any further until I return the balance of minerals, meanwhile the organic introductions into the tank are unchanging (fish are still pooping, food is still being fed.)

Thanks for the discussion!

Well you weren't asking me but I will attempt to answer some of it.

Why pH and a certain value are so essential?
That question alone could fill a chapter in a book and several articles. Calcification rates increase as the ph rises. above 8.5 you begin to have problems with precipitate plugging pumps, coating heaters etc, at about 7.6 decalcification can occur.

Hopefully someone will expand on, this I have to go.

 

[Wy Renegade]

Sorry, I admit I haven't read the entire thread-I read the original post by Anthony, then his response, and got sorta bummed out by the lack of information I was hoping to get out of it.

What I've always understood by research, stripped water (RO) should read around 7, which is "true neutral" (at least in every chemistry class I've ever taken)

Actually, distilled water is pure water (technically pH 7 until it reacts with CO2 gas), and if produced using modern distilling methods is more pure than RO/DI water. The use of copper tubing in some of the older distillers resulted in copper ions leaching into the water, thus resulting in contaminated distilled water.

Not a problem, as I anticipated, the explaination for the acidity of distilled water is essentially the same as that given for RO/DI water. Acidity through the binding of CO2 molecules from the air, because of a lack of other buffering agents which are typically found in harder water such as calcium and magnesium ions.

So basically, if in fact we introduced our RO/DI water into a vaccum and kept it from ever having air contact, it would in fact have a pH of 7, as we are lead to believe in any chemistry or related science course. However, since pure water is relatively unstable, exposure to CO2 in the air quickly causes it to become acidic in nature.

can't imbed for some reason, but here's an image worth a glance
http://ga.water.usgs.gov/edu/graphics/phdiagram.gif

When the water is further depleted, it becomes "acidic" -distilled being one of these. By distilling-where only the pure H20 molecules are ideally collected from the steam vapor, there is a reduction of anything that is not H20 in the end solution. Thus the greater acidity of the distilled water.

This site had some good info
What Is the pH of Distilled Water? | eHow.com

and excerpt

Some good info there. Interestingly enough, I think we're all on the same page, the question I'm starting to zero in on is more in regards to pH. If I understand the earlier information correctly, the issue with baking soda is that it cannot raise pH above 8 (given that it has a pH of 8), and therefore buffering with a better buffer is going to raise the pH higher and therefore prevent the introduction of "acidic" water (as a result of CO2 uptake). Does that sound about right?

 

[skinz78]

WOW great info! I am learning a lot from this thread!

As much Alk as I have been adding to my tank I can't get my PH to go above 8.15. I am wondering if I should drill through the wall and run my skimmer air line outside to help raise this a bit?

 

[VegasRick]

Vegas,


I am not sure I completely understand this,.

Thats why we are having this discussion. And the article I posted basically said what Anthony said, only in a different way and in greater detail. So those who didn't understand it the way he said it might get it this way. It was also saying what AJ was saying. Because the ph of pure water is neutral, it is very easily changed. It becomes acidic just by being exposed to the co2 in the air. In the same way it quickly becomes alkaline when added to the system. And unless you are dumping a lot of ro in your system at once, you aren't shocking your corals.

No where did I ever say not to use buffer. I feel that it doesn't matter whether its added to the top off water or directly to the sump. As long as it is added and levels are maintained at consistent values. What I did say was I thought kalkwasser was a better choice and is what I use.

 

[beaslbob]

WOW great info! I am learning a lot from this thread!

As much Alk as I have been adding to my tank I can't get my PH to go above 8.15. I am wondering if I should drill through the wall and run my skimmer air line outside to help raise this a bit?

You should dose alk buffers like baking soda until alk (kh) is correct. Not to raise pH.

your pH regardless of the kh will be much above that value if macro algaes are consuming the carbon dioxide. with the kh at correct values the light off pH drop will be much less


my .02