PH of RO water

Discussion in 'Water Chemistry' started by denMk, Apr 25, 2009.

to remove this notice and enjoy 3reef content with less ads. 3reef membership is free.

  1. denMk

    denMk Flamingo Tongue

    Joined:
    Oct 15, 2008
    Messages:
    108
    Location:
    St Louis, MO
    I have maintained marine tanks from 12 gallons to 125 gallons at various times over the past 15 years. Typically moving is what has caused me to go up or down in size and/or go without for time periods as well. I have always been able to maintain healthy and successful tanks using conditioned tap water. I always have live sand, live rock, but only soft corals, i.e. zoas, palys, mushrooms, leathers, etc.

    Recently, I decided to begin making water changes and using top off water that is RO/DI purchased from my LFS just to see if there is any difference in how my tank thrives. When I brought the water home I tested the PH in the unsalted top off water to see how close it was to my tank. I was surprised to see it was only 7.4 compared to my tank water and water from my tap that are 8.4. I have never noticed anyone talking about having to raise the PH of their RO/DI water to suit a marine tank. Is the water I received unusual, or is it normal to have to treat RO/DI water to increase PH?
     
    denMk, Apr 25, 2009
    denMk, Apr 25, 2009
    #1

    2. Click Here!

  2. inwall75

    inwall75 Giant Squid

    Joined:
    Sep 10, 2003
    Messages:
    7,172
    Location:
    America
    pH of RO/DI water that is 100% pure would be 7.0
     
    inwall75, Apr 25, 2009
    inwall75, Apr 25, 2009
    #2
    1 person likes this.
  3. inwall75

    inwall75 Giant Squid

    Joined:
    Sep 10, 2003
    Messages:
    7,172
    Location:
    America
    inwall75, Apr 25, 2009
    inwall75, Apr 25, 2009
    #3
  4. sostoudt

    sostoudt Giant Squid

    Joined:
    Jul 9, 2008
    Messages:
    5,958
    Location:
    Chesterfield, VA
    curts right 7.0 is pure water, and the teachers thought i didnt listen in middle school science. although to be fair was playing a gameboy at the time
    the salt mix adds salts that are suppose to raise the ph to around 8.2
     
    sostoudt, Apr 25, 2009
    sostoudt, Apr 25, 2009
    #4
  5. denMk

    denMk Flamingo Tongue

    Joined:
    Oct 15, 2008
    Messages:
    108
    Location:
    St Louis, MO
    Obviously I'm not a chemist! ;D And the 7.4 measure is the lowest my test kit would go and by color comparison wasn't exact either, LOL. So the water might actually be 7.0. So all I was ever worried about was if the PH was right and after all of these years never had to buffer it in any way. Glad I thought to check it before using however! Another proof point that you're never too old to learn something!
     
    denMk, Apr 26, 2009
    denMk, Apr 26, 2009
    #5
  6. SAW39

    SAW39 Ritteri Anemone

    Joined:
    Nov 6, 2005
    Messages:
    635
    Location:
    Northern Virginia
    The pH of your fresh, RO or RO/DI water doesn't matter. As Sostoudt implied, what matters is the pH of your mixed salt water. Check it before adding it to your tank. In my opinion, if the salt water is at room temperature and the pH is not above 8.0, you should add some buffer before adding the water to your tank.
     
    SAW39, Apr 28, 2009
    SAW39, Apr 28, 2009
    #6