The ole evil buffer product question

[Karlsbad]

OK so a lot of people use RO water. I want to start using 50% RO water. The phosphates in my tap water are 1.5 ppm up from 1 ppm two weeks ago and I suspect they may have been fluctuating even higher for some time.

Everytime buffer products are mentioned its a freaking lynch mob here. But there has to be a large number of closet buffer users given the number of RO users. I want something simple(ie not adding crushed coral or the moss from the lowermost 3 feet of a tree that's only found in the upper 1/7 of a remote island)and reliable and stable that won't hurt my little buddies and won't add evil phosphates. I don't want to debate or explain my reasons for using RO water if you don't mind, but can I get stable results using some good brand bicarb product carefully, say like RO right and a Kent or Seachem buffer and letting it sit and aerate between the addition of RO right and the pH product? I'm wanting to add 15 gallons tap water and 15 gallons RO water weekly. My tap (and current tank)water has a ph of 7.8, 120 ppm GH, and alkalinity of 150 ppm.

I think I'll be buying a fancy pen too :)

[travelinman1969]

If you use 100% RO then RO right will be okay. But that can be expensive. Here is what I do. I add about 90 % RO and 10% tap, treated of course. My water is so hard, anything more than that, I get a huge ph swing. I have kept my parameters at the following:

ph- 7.2
gh-75
kh-120

I add RO right every other water change, which for me is about every day. I'm starting to think the RO right is not doing me any good, but I'm afraid to change my routine.

[Karlsbad]

Err I thought RO right was just a hardness product. Does your RO water come out of the RO unit at 7.2 ph?

[RTR]

There is no way to get a valid pH right out of a high-rejection rate RO unit producing very low TDS (high purity) water. Ditto for DI water. Without RO right or comparable mineral mix (~Equilibrium, etc.), you cannot do a valid pH.

If you are set by pressure and rejection for only moderate TDS output, you can read pH.

There have to be some minerals present to read pH.

Folks - including me - poo-poo the routine use of buffers in tap water because 1) many are phosphate based, causing more problems than they cure and 2) because they tend to be very short-lived, increasing the TDS of the water until diluted out by partials for short effective lives. Too many folks have the mistaken idea that all fish must be kept at some magic pH close to the pH of their native water. This is false. Most fish are quite adaptable to water parameters. Some, particularly blackwater fish, do need low-GH water for breeding as the egg membranes are far more sensitive to mineral content than the adults. Over-riding the pH of tapwater by adding more material to the water is not, repeat not, reducing the mineral content of the water and is therefore counter-productive.

Reconstituting some mineralization in RO/DI water is not the same thing as adding buffer to tap water, it is needed in a captive closed ststem as straight high-purity RO/DI is not suitable for long-term support of fish.

Apples and oranges, don't get the two situations confused.

[happychem]

Originally posted by RTR
There is no way to get a valid pH right out of a high-rejection rate RO unit producing very low TDS (high purity) water. Ditto for DI water. Without RO right or comparable mineral mix (~Equilibrium, etc.), you cannot do a valid pH.

If you are set by pressure and rejection for only moderate TDS output, you can read pH.

There have to be some minerals present to read pH.

Why is that? Granted I'm not up to speed on my pH indicator theory, but if you were able to remove all non-water molecules, should the water's natural equilibrium set up a pH 7.0? The indicators measure H+, not minerals. Or are you just refering to CO2 equilibrium and the need for it to re-equilibrate post RO?

[Karlsbad]

Originally posted by happychem


Why is that? Granted I'm not up to speed on my pH indicator theory, but if you were able to remove all non-water molecules, should the water's natural equilibrium set up a pH 7.0? The indicators measure H+, not minerals. Or are you just refering to CO2 equilibrium and the need for it to re-equilibrate post RO?

I could be wrong here, tell me if I am, but I think DI water comes out neutral and ends up around 5.5 - 6 after C02 dissolves from it or permeates into it or does some other thing that CO2 does. Don't ask me why. I actually thought that was the case with RO water as well, which is why travelinman has me confused being that he just adds RO right, which I understood to not directly affect PH other than providing hardness, yet he has a pH of 7.2.

[artemis]

Karlsbad, how hard is your tap water? You may not need to add any buffers at all. If you were planning to use 100% RO/DI water, you'd definitely need to use a buffering agent (and add trace minerals back to it as well) because being pure water it would have essentially no buffering capacity - but you're planning to use 50% tap water/50% RO water. If your tap water is even moderately hard, when you mix it with the RO water it will add all the buffering capacity you need.

[happychem]

Yeah, I understand that. If you use DI, then you remove carbonate & bicarbonate. CO2 equilibrium shifts, lowering pH.

What I'm wondering is why RTR said that you can't measure pH without minerals. I can understand that the pH you measure will be different than post-CO2 equilibrium/addition of RO right or minerals. But can't confuses me.

[Canuck]

The problem lies in the fact that there are no buffering agents in pure RO water. A tiny bit of CO2 dissolves in the water forming carbonic acid then the pH plummets, the water comes in contact with something alkaline then the pH soars. Each pH measurement you get can be valid, but it can also change radically in a few minutes.

HTH,

Dave

[RTR]

Happychem - if you have high-quality water in the lab, try it - you need eletrolytes for the pH probe to work. We always used resistance - it will still work up to WFI (which we generated and used for our cultures). Probes are too erratic in low TDS water, cannot be validated. Direct electrical resistivity can be calibrated.

[anonapersona]

In other words, breathe on the water and you change the pH.

[Karlsbad]

Is it true that 17ppm TDS = 1 kH?

[happychem]

Yeah, I understand it for pH probes/electrodes, and I follow the reasoning that without buffer the pH would be unstable. But what about pH indicators, say, bromothymol blue which changes colours around pH 7?

I suppose the phrasing of my question should have been: when you say that you "can't" do a pH reading, do you mean that you can't get one that would be a useful reading due to the lack of buffer, or physically can't? I know that pH probes cannot, but since most hobbists don't have pH probes, I was thinking more along the lines of pH indicators.

[RTR]

You get meaningless numbers from high purity water other than by electrical measures. Why would anyone try if the "data" is meaningless? Far worse than not measuring is measuring something which cannot provide a useful result. Bad data is not better than no data, as it can be misleading.

[happychem]

Yup, agreed about that. Thanks for clearing that up. I thought that I was missing something big.

[travelinman1969]

Okay, I've gotten more confused as I've watched this thread. If I'm getting this right, and I'm not a water rocket scientist, The buffering is what keeps the ph stable. Is my adding the 10% tap water keeping the ph stable? Does the tap water have the buffering agents I need? I used to use bottled water all the time at my last house because of the water, and never added tap water I did add RO right there also. Was I in danger of a major ph swing? I take it the RO right is not adding the proper buffering agents?

Most people might think that the ph doesn't effect a fishes behavior but I beg to differ. I had to replace my RO stystem and had to use tap water for about a month. In that time my arowana tried to kill himself at least 4 times. He damaged himself pretty bad. He's much better now, but at the time of using the tap water the ph rose to 8.0. Since going back to the RO and getting the ph back to 7.0-7.2 he has calmed down 10 fold. I understand that most species don't care about ph but it appears this big dog does. Even my oscars don't seem to be as aggresive lately.

RTR, is there any good reading material that I can read to help get me to understand all this better?

[Karlsbad]

travelinman what is the ph of the water out of your RO system after it sits for a couple of hours? My understanding is that RO right gives you hardness(buffering) which would allow ph to be stable. I think there's also some factor that pH is not linear so maybe its that your 8.0+ tap water dilluted by 90% causes your 7.2 solution?

You know I've noticed that some people refer to buffer products as pH adjusting products, and some refer to buffer as trace element products such as RO right or Aquarium Pharmaceuticals Electro Right.

[RTR]

For measurement of pH in high purity water, you would need a laboratory handbook, and it does require some chemistry/physics background. Thry the local library research desk and they can likely get you a loner from an area university.

For a crude first view of pH and alkalinity, try:

http://www.tomgriffin.com/aquasource/hardwater.shtml

but that may not be what you want, and it is not light reading.

[travelinman1969]

Well, from what I've seen you guys saying, I can't get a true ph reading from RO water. However, Going by the numbers that I do, 90% RO 10% tap and knowing that I add RO right, which will not change ph, I think, Then I would say the RO puts out a 6.8-7.0 ph. My ph at my old house was 6.8. I'm adding some tap water here and it's a bit higher at 7.2. The water here is pretty hard also, but not as bad as my old house.

RTR, I'll take a look at the material tomorrow. As much as I have invested in these tanks it's in my best intrest to understand this better, especially because of the fact of using RO water. Not light reading? Have you ever read a Clancy novel? LOL!! I do all the time.

[RTR]

At least Clancy does not include chemical formulae, but he does deal with balances and equilibria. :o