Info Wanted On Reverse Osmosis (r.o.) Water

[shmikuk]

Just wondering if anyone could give me a bit more information on R.O. water..

I have looked for information on it but can only find it linked with information on marine set-ups. Can you use it for tropical set-ups too? My reason for asking, is because I have a tropical set-up and am looking to move home soon. I was wondering whether (when i have to empty out the tank water) i can replace it with this R.O water (not all of it, perhaps 70% R.O./30% tank). Any information on this would be much appreciated!

 

[idlefingers]

People do use RO water in tropical setups but only normally for certain fish such as Discus. RO water is very soft which is what Discus like (I'm sure there's more reasons but I can't think right now).. The problem is that RO cleans the water almost too much.. it's so pure that you have to put certain minerals back into it. I think it changes the ph of the water as well but am not sure. With marine, the salt you put into the RO water makes it perfect.

Unless you have fish which require it, IMO using RO on a tropical tank is unnecessary and expensive.

 

[backtotropical]

Agreed. RO water has a PH of about 4 - 5. You would then have to raise the PH before use with your tank. You do this by adding back in essential trace elements which the RO unit removes. This can be expensive and time consuming. Unless you are keeping Discus or something similar, which would appreciate it fully, it's probably unnecessary IMO.

 

[SNAIL]

I've been using 100% RO water for a few years now on my tropical freshwater tank. I do have live plants, fish, and inverts. Depending on what your setup is, it is usually okay to use RO water. As the others have mentioned, RO water is soft. RO is the process of passing water through a membrane to remove elements, contaminents, minerals and microbs as well. You do and should add trace elements to your tank when using RO water. I found it to be beneficial to my tank. I have never had problems with algae from the day I set up my tank 4 years ago.

 

[Fwapp]

Hi,

I use RO in my planted tropical tank, as the nitrate levels in my tap water are really high. I 'cut' the RO with tap water to get the pH, etc where I want it. It works out at about 50 liters RO to 12 liters of Tap.

HTH!

 

[Bignose]

Agreed. RO water has a PH of about 4 - 5. You would then have to raise the PH before use with your tank. You do this by adding back in essential trace elements which the RO unit removes. This can be expensive and time consuming. Unless you are keeping Discus or something similar, which would appreciate it fully, it's probably unnecessary IMO.

RO water actually has a pH of exactly 7.0. But, since it is so pure, if any impurities happen to get in the water, the pH can change a lot really quickly. This may include some residue on the tubes you tests pH in, for example.

You have to put minerals back into the RO water, otherwise over time you will kill anything that lives in it. Because RO water is so pure, the minerals in the fish's bones, body, etc. will leach out of the fish. However, RO water is also a blank canvas, so you get to put back into the water whatever you want. It is perfect for people who want to know exactly what is in their water.

 

[BigC]

http/www.ro-man.com/faq-pro/index.php?ac...d=003&id=37
Regards
BigC

 

[shmikuk]

Agreed. RO water has a PH of about 4 - 5. You would then have to raise the PH before use with your tank. You do this by adding back in essential trace elements which the RO unit removes. This can be expensive and time consuming. Unless you are keeping Discus or something similar, which would appreciate it fully, it's probably unnecessary IMO.

RO water actually has a pH of exactly 7.0. But, since it is so pure, if any impurities happen to get in the water, the pH can change a lot really quickly. This may include some residue on the tubes you tests pH in, for example.

You have to put minerals back into the RO water, otherwise over time you will kill anything that lives in it. Because RO water is so pure, the minerals in the fish's bones, body, etc. will leach out of the fish. However, RO water is also a blank canvas, so you get to put back into the water whatever you want. It is perfect for people who want to know exactly what is in their water.

I have in the tank 3 dp's (dwarf puffers), kuli loaches and a few otto's. I have checked my local info on dp's and it said that they prefer a ph of at least 7.0.. i am not quite sure what to so now.. Maybe i should stick with tap as i normally do.

 

[andywg]

RO water actually has a pH of exactly 7.0.

I am not sure how this relates, but wiki states the below which may mean the "exactly" should be removed:

Neutral pH at 25 °C is not exactly 7. pH is an experimental value, so it has an associated error. Since the dissociation constant of water is (1.011 ± 0.005) × 10−14, pH of water at 25 °C would be 6.998 ± 0.001. The value is consistent, however, with neutral pH being 7.00 to two significant figures, which is near enough for most people to assume that it is exactly 7.

However, I may have completely misunderstood what it is saying.

 

[Bignose]

Well, whether it is 7.0 or 6.998, it definitely isn't 4 or 5

It takes some pretty beefy equipment to get a reading to 3 significant figures, all the stuff I've ever used in the lab only reports tenths, and those probes were usually at least a hundred dollars. I can only imagine how expensive a probe that measures thousandths must be.

 

[andywg]

Well, whether it is 7.0 or 6.998, it definitely isn't 4 or 5

It takes some pretty beefy equipment to get a reading to 3 significant figures, all the stuff I've ever used in the lab only reports tenths, and those probes were usually at least a hundred dollars. I can only imagine how expensive a probe that measures thousandths must be.

I'd be surprised if anyone really bothers. From what I can gather the theoretical "pure" water value is actually incorrect as pure water contains nothing to measure with and in order to read what the pH involves introducing some of what will be measured, so it is no longer pure. Secondly, it seems that the value is derived by theoretical maths, rather than by actual measurement.

 

[Dave Spencer]

I'd be surprised if anyone really bothers. From what I can gather the theoretical "pure" water value is actually incorrect as pure water contains nothing to measure with and in order to read what the pH involves introducing some of what will be measured, so it is no longer pure.

At work, we measure the conductivity of the output from our water treatment plant, as a function of pure water being an insulator. The final product comes out at .002 microsiemens/cm which is fairly pure water, and will consequently have a pH of nigh on 7. My guess is that if you can`t pass a current through it, the water must be pure.

We then adjust the pH up using ammonia, but only measure the pH to two decimal places before admitting it to the boilers. The nuclear power or microprocessor industries might find it necessary to measure pH to four places, but I`m not sure.

Dave.

 

[ArauraDiscus]

How the heck could RO water have a ph of 4-5? Thats ridiculous. Didn't we all learn in school that water purely has a Ph of 7.0-7.2? I though the PH scale was based off the neutral Ph of water. RO water is 99 percent pure water... SO it's Ph is 7.2.


Thats almost as ridiculous as me trying to recite the alphabet backwards, which I've tried, and I get all the way down to J and then I start singing the alphabet song because I can't help it.

 

[andywg]

How the heck could RO water have a ph of 4-5? Thats ridiculous. Didn't we all learn in school that water purely has a Ph of 7.0-7.2? I though the PH scale was based off the neutral Ph of water. RO water is 99 percent pure water... SO it's Ph is 7.2.

RO water has no buffering capabilities, meaning it absorbs almost anything. Consequently it absorbs carbon dioxide from the air which lowers the pH to around 5.7 IIRC.

 

[backtotropical]

RO water has no buffering capabilities, meaning it absorbs almost anything. Consequently it absorbs carbon dioxide from the air which lowers the pH to around 5.7 IIRC.

As said, RO water has no buffering capacity and will therefore absorb almost anything, it will even, to an extent take on the PH of the container which it is in or the air.

I agree that absolutely pure water should have a PH of 7, and i conceed that maybe PH4 is too low for most situations, but that pure water starts absorbing impurities as soon as it leaves the RO membrane, usually lowering the PH to below 7.