Why would you buffer topoff water from an RO/DI?

[apos]

I'm getting an RO/DI from filterguys, and I've been reading up on how to intregrate it into my system. Basically, I'm wondering how it affects buffering. I currently use Instant Ocean salt, which sets the Ph and Alk and so forth supposedly to the right levels, and I've been thinking of upgrading to Reef Crystals as I add more corals.
But I've read conflicting information on how the use of RO/DI water will affect this. As I understand it, the water will have virtually nothing in it, including the minerals that help keep ph stable. Hopefully my salt mix won't suffer from this too much, and will still have room to compensate. But do you buffer topoff water? I would assume that evaporated water would concentrate what's left: i.e. only h20 evaporates, not buffer. So adding back pure water shouldn't ultimately change anything, right? Or will the sudden addition of so much unbuffered water hurt the system any?

 

[scopus tang]

Originally Posted by Apos
http:///forum/post/2480759
I'm getting an RO/DI from filterguys, and I've been reading up on how to intregrate it into my system. Basically, I'm wondering how it affects buffering. I currently use Instant Ocean salt, which sets the Ph and Alk and so forth supposedly to the right levels, and I've been thinking of upgrading to Reef Crystals as I add more corals.
But I've read conflicting information on how the use of RO/DI water will affect this. As I understand it, the water will have virtually nothing in it, including the minerals that help keep ph stable. Hopefully my salt mix won't suffer from this too much, and will still have room to compensate. But do you buffer topoff water? I would assume that evaporated water would concentrate what's left: i.e. only h20 evaporates, not buffer. So adding back pure water shouldn't ultimately change anything, right? Or will the sudden addition of so much unbuffered water hurt the system any?
No, your right, only the water evaporates so adding RO water should have no effect on the buffering ability of the tank. Keep in mind however, that an RO system is not the same as a distilling system in which everything is removed from the water. The RO system does still leave somethings in the water (usually in the form of ions which are bonded with the free hydrogen and hydroxide ions in water). As a result, RO water is less chemically aggressive than distilled, and will not leach important chemicals like calcium out of your system. While this leaching effect is very slow, it does occur.

 

[apos]

You mean RO and RO/DI, or just RO? I'm getting an RO/DI system that will have near 0 TDS.

 

[nereef]

RO DI water should have nothing in it but water. you are right not to buffer topoff water, since pure water doesn't affect pH of any solution.

 

[scopus tang]

Originally Posted by Apos
http:///forum/post/2480800
You mean RO and RO/DI, or just RO? I'm getting an RO/DI system that will have near 0 TDS.
Sorry, wasn't clear lol! RO/DI is fine. Was talking pure distilled water vs. any type of RO water in general

.

 

[briand7878]

Test your p.h. when it comes out of the ro/di filter. I bet it is really low. I still use it in mine with no problems though. oh and never ever do a fresh water dip with ro water. That is an instant death sentence.

 

[apos]

Been reading more on this. According to the wetwebmedia guys, the best practices is:
1) RO/DI water will be acidic due to lots of CO2. Thus you need to heavily aerate it for 6-12 hours to drive off the CO2 and neutralize the PH
2) At this point you still might not want to add the water in as topoff, because the water will "use up" the alk that's in the tank from your salt mix. This is, they say, why so many people battle flat alk and ph problems. You thus might want to buffer the water a bit first.
3) Most artificial salt mixes have enough alk in them and are based on the assumption of pure water (Instant Ocean says this, for instance) such that they may not need any extra buffer first.
So I'm still a little unclear. I know using non-buffered water isn't going to explode my tank all of a sudden, but it does sound like it can flatten your alk and hence risk your weakening your ph stability.
Anyone have any more opinions on this?

 

[gmann1139]

Apos -
I used RO water with Instant Ocean Salt. Alkalinity is usually 2.5 - 3.0, which is within range, and pH is 8.1 - 8.2. Not optimal, but fine for a FOWLR.
I do water changes biweekly, 20%. I've found the alkalinity does drop week to week, but only .25, so no problems.
To answer Brian D, if the pH of the RO/DI water is anything but 7.0, change the filters.
Also, a dip in RO Water is the same as a dip in any freshwater. I've done 5 minute baths in the past to combat ich, and the fish was/is fine.

 

[apos]

Originally Posted by gmann1139
http:///forum/post/2486630
To answer Brian D, if the pH of the RO/DI water is anything but 7.0, change the filters.
I disagree. Purified water is naturally acidic, which is a major reason why it needs to be aerated after being produced before use. It should be nearer to neutral after aeration.
Originally Posted by gmann1139
http:///forum/post/2486630
Apos -
I used RO water with Instant Ocean Salt. Alkalinity is usually 2.5 - 3.0, which is within range, and pH is 8.1 - 8.2. Not optimal, but fine for a FOWLR.
I'm never quite sure what people mean when they talk about alk. My understanding was that it should be in the 6-11 range, and that ph should be 8.4-8.6 ideally for reefs: I didn't know that FOWLRs are different in that regard, but I guess it makes sense now that you mention it.