Buffering RO/DI?

[skinz78]

I have heard of this before and wondered about it ever since but never have done it. Anthony Calfo just recommended it in one of my other threads so I thought I would bring it up.

Does anyone else do this and if so how do you go about it?

I purchased a bunch of stuff from a fellow hobby'st who was getting out of the hobby and got 3 2lb containers of Kent Osmo-Prep and just filed them away but I am thinking of using them now.

 

[btkrausen]

I've honestly never heard of it in 6+ years of reefing. Interested to find out more....

 

[Anthony Calfo]

Do you want me to chime in with more of my perpective or are you just looking for others for consensus presently?

 

[skinz78]

Actually I am looking for both!

 

[Anthony Calfo]

All good, either way, my friend. I'm not one for taking the word of authorities or so-called authorities as gospel, regardless of their creds. Good information gathering is indeed about an informed consensus. And yet, if we take a consensus on a topic like this, you'll find that most folks do not reconstitute their demineralized water. Which would be fine if they could justify it, but like so much of hobby habits...its founded on misinformaton or an outright lack, thereof.

At the end of the day, what matters is adequate and stable mineral levels in the aquarium. And the fundamentals of what we are talking about here is maintaining adequate if not strong pH and alkalinity for better rates of calcification, larger bioloads, or simply the burden (steadily increasing dissolved organic) of a maturing tank in time).

These realities, made worse still by not uncommon scenarios such as a lack of water changes (reflecting the impact of unabated production of organic/nitric acids fro bioactivity), use of calcium reactors (CO2/carbonic acids also chewing up alkalinity)...

Erhhhm, I could go on. But you get the picture. The nature of aquarium keeping (all...fresh salt and brackish of course) is an acidic slide. We have to maintain pH and alkalinity (so much more important for pH stability) for the system we choose to set up.

Compound this by the reality that a lot of buffers are made, well...cheaply. Relying principally on sodium bicarbonate which was fine as a staple for marine aquarium keeping in the 1970's (example) when the few organisms hardy enough to survive archaic import and holding systems would in fact live in an aquarium sadly maintained with baking soda as a buffer (read: pH levels chronically under 8.0 and ultimately never able to go higher than 8.3). Its no coincidence that buffer manufacturers back then conveniently misreported (ahem) and promoted/advertised (cough) that a healthy marine aquarium should be kept between 8.0 and 8.3. To offer a better buffer than relabeled baking soda would have cost more, made less (profit) and sold less to tiny market of consumers not ready to spend big bucks like we do today. Ironic historical aside: the pushers of cheap buffer would ultimately place the responsibility for buffering on dolomite substrates or calcite...ironic because they do not dissolve readily until the pH drops to around 7.6. LOL (at which point you have a bigger problem than quantifying which was the better buffer, your cheap alkalinity booster or the crappy substrate you just bought.) [Note: aragonite will dissolve at a pH over 8.0...well over actually. Read: a better buffer support if you choose to rely on substrate for part of the duty]

So, we (hobbyists) shop and debate and argue online about sea salts and which has the higher pH and which has better Ca or Alk on mixing...without talking about the source water we are using to mix it up? Erhhhhm...?!? And salt some brands of which, albeit tried and true - all respect indeed - have not fundamentally changed their recipe in a gazillion years. Meaning...they formulated these salts at a time when almost nobody used purified water.

At the end of the day, it really doesn't matter how we buffer the water and insure better pH and alkalinity, so long as it gets done safely and hopefully consistently over time. And yes, there are sea salts that are formulated for use with RO or otherwise demineralized water.

But a majority of aquarists struggle with pH problems; very few consistently have a ph that doesn't drop below 8.3 at night let alone above it by day! And if you add raw, demineralized (RO/DI) evap water to your souring reef gallon by gallon day after day...how to you reckon that amelioration of water with 300+ ppm mixing with water with near zero ppm of hardness? For example...10 gallon (actual volume) of sump water at 10dKH gets 1.5 gall of evap top offf water each day with a pH under 7 and a dKH near nil, what do we expect the readings to be after the mix? Lessoned, indeed by the total volume of the system (maybe a 90 gall display this example). But day after day raw, sour, "pure" RO?DI water giong in and adding to the overall pressure on the system to keep pH and Alk up.

The simple fact is that demineralized water (RO/DI) is extremely unstable at any pH it comes to you (even sometimes even it is over 7). By aerating it (driving off CO2/carbonic acid) you will raise the temporary pH. And by buffering it slightly, you ease the burden and hedge your bets on the inevitable processes in aquaria ongoing after your water exchange that will bring down pH and alkalinity. There is no disadvantage to remineralizing your ro/Di water before it is used for evap top off or salting.

That is, I think...my short answer

FWIW, I do still use the old fashioned "tri-buffer recipe" (bicarb, carb and a borate) for dirty or bulk work...but I prefer to use well engineered products from thoughtful companies like Brightwell Aquatics and Seachem for this purpose.

 

[Sasquatch]

I love the "acidic slide" that may well be the most concrete explanation Ive ever heard, Thank you Sir!

 

[skinz78]

WOW I think I got it now. Do you think there is a possibility that this may be the cause of a major problem in one of my old reefs? I lost a lot of clams all at once and all unexplained. They just closed up slightly one day and the next day they were dead.

I have never watched my PH, I have just watched my Alk assuming that if my alk was acceptable then my PH should be too.

 

[Anthony Calfo]

Hard to say in hindsight, but my experience is that most aquarists at some point (often a long time) have a moderate to severe problem sustaining adequate pH. The recent unhealthy obsession with sky high calcium levels has made the problem worse (stiffling Alk levels and in turn tank stability indeed fending off the acidic slide).

Remineralizing your RO/DI water isn't required any more than a skimmer is required for a healthy tank. But the lack of stability in RO/DI water must somehow be accounted for. To aerate and buffer it in advance is just one of the many small, habitual things we can do to lessen the overall burden of sustaining strong system pH and Alk levels.

The raw evap water that goes into our tanks alone daily/weekly (without factoring wekly/monthly water changes) is a lot of "sour" water that takes its toll on an already taxed pool of alkalinity.

 

[skinz78]

Well you have me convinced, I am going to start using this stuff up that I have and then get some Brightwell when it is gone.

I take it that you recommend to buffer the water and aireate it as well? Is it alright to just do this with a powerhead maintaining surface agitation of the water?

What are your thoughts of using the Kent Osmo-Prep, should I use it or get something better?

 

[jski711]

So what product do you add to the water? I'll try anything once. Thanks for the "short" yet informative answer.

 

[jski711]

Also what effect would this have if topping of via kalk reactor.

 

[ksc]

If you are dosing 2-part you are effectively buffering your top off. If your ph is low simply use soda ash instead of the bicarbonate. Those buffer products will make it a lot harder to balance your system (I'd bet that these products are predominately baking soda and soda ash). There's nothing wrong with running your tank at ph 8-8.4...

 

[Anthony Calfo]

Interesting question...if all your top off water is saturated with calcium hydroxide, you do not want to aerate or buffer it. Both will lead to the formation of insoluble calcium carbonate (chalky film you see on the surface of your mixing container, even th salt mixing bucket to an extent, etc.

So if raw demineralized water feeds the kalkreactor...you have the advantage of the caustic (hydroxl) solution tempering the likely acidic (RO/DI) source water while being calcium rich. What you DO NOT have (still) is any alkalinity to that feed. That, you will have to come up with some other way. With a an aragonite dsb (dissolving and partly mineralizing the water daily) you will get some help. But adding buffer (always during daylight...never at night) you will meet your Alk needs.

Interestingly, people that do not mix kalk with acidic source water find that faith dosing of kalkwasser or kalk slurries each night can nearly or fully eliminate the need for dosing buffer products. Not because because kalk directly supports alkalinity (it does not), but because its caustic nature neutralizes carbonic acid, nitric acid, etc produced in aquaria that would otherwise be a burden (chewing up) alkalinity. Such systems do just fine with some kind of aragonite and a reasonable water change schedule.

You see, many factors involved here. Theres no clear answer for everyone.

For me, I'm currently using Brightwell and Two Little Fishies. In the past I have very happily used SeaChem as well. There are other wonderful companies too.

The 2 (or 3) part liquid type supplements are actually quite good(!) and highly recommended (versus kalk + dry buffer) for people with smaller tanks especially. It's safer and easier. But they are markedly less cost effective. Though my fishroom has scaled back to less than 3K gallons, it's still too expensive for me to use liquid buffers.

 

[AZDesertRat]

Hey Anthony, this is AJ, the former Pres. of the old Desert Marine Society in Phoenix, its been a long time guy! Good to see you here. I miss the good times we had with you and Bob Fenner.
How do you measure the amount you buffer? Since RO/DI has so few mineral ions measuring the pH is almost impossible so a pH reading is just about worthless. I have always been taught RO/DI quickly takes on the pH and other characteristics of whatever you add it too with little effect on pH. In my mind buffering the pH is a waste.

 

[droblack]

I've always wondered about drinking acidic RO water, and wanted to buffer it for myself and the reef.

 

[Anthony Calfo]

hey, AJ...great to hear from you, indeed!

Respectfully, I must say, I think you really don't understand alkalinity (as a measure of hardness or pH), my friend. You've made some rather remarkable statements!

RO does not "[take on the characteristics of what you add to it without affecting pH]." You can see that is wildly not the case by adding muriatic acid or a measure of calcium hydroxide to a sample of RO water, for starters XD.

Lets be clear though: demineralized water, as we typical prepare it with hobby filters and also pending the source water, condition of the RO membrane or state of exhaustion of resin, etc. can variously have a wide range of pH. But if said water is mostly pure (near fully demineralized), then its pH will be unstable, regardless of what reading you get. Unstable...meaning VERY easily changed (and thats a dangerous thing to most aquatic life forms).

To stabilize it, we must raise the alkalinity (hardness, if you will). And that is the essence and benefit of buffering RO water. I can't reckon how you see that as a waste, my friend?

Even aquarium hobbyists of the most acidic, softwater loving species (wild discus fish for example) are faced with the very same problem. They may keep species that naturally hail from and fare best in ultra soft and ultra acidic water (near 6.0 or even lower, less than 10ppm TDS)...but such fish cannot be safely kept in aquaris that way because that water is unstable. Unstable IN AQUARIA as a closed system where food and fish waste are in greater concentratio (the acidic slide) than the sum total of the Amazon river basin (soft, acidic...but HUGE and not easily changed quickly, unlike aquaria). Breeders that try to walk the fine line of ultra soft and very acidic water can see what appears to be an otherwise "stable" tank suddenly turn sour and dire fast (mere minutes to hours) when the minimal alkalinity is exhausted and pH plummets (causing acidosis and rapid death).

Aquarium water has an always uphill battle to insure stability. Buffering your unstable RO or DI water is one of the fundamental ways to relieve pressure on the pool of Alkalinity.

Its safer to temper that raw water in reserve separately too (versus ignoring it and just dosing the tank later) because the raw water is not stressing the sump or tank fauna with a weak chemistry (on influx of sour evap water or weak salted water).

 

[Anthony Calfo]

Droblack...indeed the bottled water sellers have a target pH as well. They commonly use RO (on tap water actually) and then remineralize it for taste. Drink from a bottle of distilled water and then from a bottle of spring water. You can tell the difference without a pH test kit if you have a tongue. LOL

 

[Dan Rigle]

Very interesting Anthony.I have really been ignoring tank PH in the last few years mostly due to the fact that when I tried to manipulate it with buffers and Kalk I noticed negative results from the instability caused by the methods used.Buffering the RODI water was something I never tried and is worth a bit of thought.My tank PH ranges from 7.8 to 8.2 if I am lucky and have some fresh air in the fish room rather then the stale PA winter air.Do you suggest adding some cal rx media to the rodi vessel or some commercial buffer.If adding commercial buffer,how to calculate how much of a given product.

Last time i tried adding kalk as all evap i ended up with issues over time.very high alk and some rtn along with loss of all refuge algae.
Not sure if this is the best method for me but if so i need to rethink the cal reactor settings to accommodate the Kalk i suspect TIA

 

[Sasquatch]

any benefit to something like an undergravel aragonite bed in the ro storage container?

 

[VegasRick]

Dan, you have a good looking tank. Obviously pH in the 7.8 - 8.2 range is working ok for you. Most people have pH in this range so it's pretty normal
I use kw as top off and a ca reactor, so you have to take in account the additions from it and adjust your reactor accordingly. But the same for just adding a buffer to your RO. You will have to adjust the reactor either way. And kw is somewhat balanced where just adding a buffer would affect kh and not ca
I think the lack of fresh air has a bigger impact on the system pH than unbuffered RO water does