PH ? When topping off for evaporation

[EasyEd77]

I tested the PH of the RO freshwater from my LFS and it tested around 7.4. I use this water to top off my tank when I get evaporation. Should I add a PH buffer to bring the water to 8.2 before I add it to my tank?

[Obsessed Reefer]

I don't think so, the environment established in the tank should stabilize the pH. I know I dont use a pH buffer, and my tank is fine. But if their RO water is testing around 7.4, you might want to be a little cautious, as pure water should have a pH of about 6.8/6.9.

[Mr. Fosi]

Pure water can even be as low as 5.5.

 

Tapwater routinely tests at 7.0-7.5.

 

EDIT: And to answer your original question; no, you don't need to and shouldn't add buffer unless you are regularly testing your alkalinity.

[filefish949]

Pure water can even be as low as 5.5.

 

Tapwater routinely tests at 7.0-7.5.

 

EDIT: And to answer your original question; no, you don't need to and shouldn't add buffer unless you are regularly testing your alkalinity.

 

 

well not exactly, if the water is PURE, at 25c the pH IS 7.0

 

what Fosi is telling you probably awnsers your question correctly

 

 

while the H+ to OH- ratio in "purified water" may be all over the map, the actual concentration of hydrogen ions and hydroxide ions in "purified water" is very low, so the impact on the pH on your tank will be negligible, mostly dilutuion

 

i like adding calcium hydroxide to my purified water and pumping it into my sump slowly, i also use a pH controler to stop the pump it the pH of my tank goes over 8.15

[Pship]

Yeah add, kalkwasser to your top off water. If you are manually topping off it might be a pita but u can buy a kalk stirrer which i would highly advise.

[Mr. Fosi]

I should have qualified my answer by saying "pure water that has been exposed to air" or "pure water at equilibrium with the air".

[filefish949]

I should have qualified my answer by saying "pure water that has been exposed to air" or "pure water at equilibrium with the air".

 

believe me, most of us know that you know (probably a lot better than me).. but it is good to give an explanation as to why...though he does not need the info now, it could very well be useful down the line

[Mr. Fosi]

Now if I could just convince a friend of mine that I know why the RO at his workplace comes out at a pH 5.5.

 

The guy is a whiz with the machines commonly found in chem analysis labs but he, himself, is not a chemist (not that I am either for that matter). He's got a GED and no BS. I tried to explain to him why water is both acid and alkaline depending on the situation and how CO2 dissolution modifies pH.

 

He just stonefaced me and said that I didn't know what I was talking about and that every chemist and chemistry text book I have ever had experience with is wrong. I told him to take some of his RO and bubble pure N₂ gas through it for a couple hours and re-test the pH, but he wouldn't have any of it. I think he was afraid that I might know something he didn't even though he has 14 years of "experience" more than me.

[Sexy Shrimp]

He just stonefaced me and said that I didn't know what I was talking about and that every chemist and chemistry text book I have ever had experience with is wrong. I told him to take some of his RO and bubble pure N₂ gas through it for a couple hours and re-test the pH, but he wouldn't have any of it. I think he was afraid that I might know something he didn't even though he has 14 years of "experience" more than me.

Quite probably - just do it for him

[Mr. Fosi]

I would, but he lives in Detroit MI and I am in Columbia SC. I know he won't believe me unless I actually do the demo right in front of him.

 

The next time he comes down for a visit, I will ambush him with it. "Let's head into the lab, there's some stuff I want to show you."

[airman_verde04]

wow, I was wondering the same thing. So topping of with my distiled water isn't going to cause the PH to drop? because I've been having to use buffer to get my levels up during the cycling. the PH seems to be the only thing now not wanting to settle to complete this cycling stuff! so add buffer to my jug of top off distiled water or no.. ???

[Mr. Fosi]

So topping of with my distiled water isn't going to cause the PH to drop?

 

Nope.

 

... I've been having to use buffer to get my levels up during the cycling. the PH seems to be the only thing now not wanting to settle to complete this cycling stuff!

 

There is a lot of stuff going on in your tank during cycling and it is normal for your pH to be depressed.

 

... so add buffer to my jug of top off distiled water or no.. ???

 

Nope. Just add the water. Do no add buffer or any other dosing component unless you are testing for it.