Low Ph and High Alk - Help Appreciated

Discussion in 'Reef Aquarium Discussion' started by Andy G, Aug 2, 2017.

  1. Andy G

    Andy G Well-Known Member

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    Hi all,

    My Ph is consistently below 7.90 during all day and below 7.7 at night according to APEX probe (recently calibrated), while Alkalinity is 12.6

    And I can't understand why this is happening.

    I already have a CO2 scrubber running into the Skimmer air line.
    Already tried opening windows which did not have any effect.

    I make 20% water changes every 2 weeks.
    Using Redsea Coral Pro salt.

    Don't want to use a buffer as my Kh is already very high.

    Any suggestions, please?

    It's an LPS tank with anemones.
    Salinity 34.4
    Calcium 450
    Nitrate 2
    Phosphates 0.02
    Ammonia 0
    Also running Carbon and GFO in reactor

    Thanks in advance
     

  2. Randy Holmes-Farley

    Randy Holmes-Farley Reef Chemist Staff Member Team R2R R2R Supporter R2R Excellence Award Expert Contributor Article Contributor

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    Buffer would be a bad choice at any alkalinity. They do very little to boost pH, despite the claims.

    If opening windows had no effect, you may just have a pH measurement error. Lots of folks have issues with Apex pH.

    If it is low, the CO2 level in the water must be high (there's no other possibility). If you air really is normal, more aeration will raise the pH.
     
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  3. Randy Holmes-Farley

    Randy Holmes-Farley Reef Chemist Staff Member Team R2R R2R Supporter R2R Excellence Award Expert Contributor Article Contributor

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    Try the aeration tests in this article:

    pH And The Reef Aquarium
    http://www.reefedition.com/ph-and-the-reef-aquarium/

    The Aeration Test

    Some of the possible causes of low pH listed above require an effort to diagnose. Problems 3 and 4 are quite common, and here is a way to distinguish them. Remove a cup of tank water and measure its pH. Then aerate it for an hour with an airstone using outside air. Its pH should rise if it is unusually low for the measured alkalinity (Figure 2). Then repeat the same experiment on a new cup of water using inside air. If its pH also rises, then the aquarium’s pH will rise simply with more aeration because it is only the aquarium that contains excess carbon dioxide. If the pH does not rise in the cup (or rises very little) when aerating with indoor air, then that air likely contains excess CO2, and more aeration with that same air will not solve the low pH problem (although aeration with fresher air should). Be careful implementing this test if the outside aeration test results in a large temperature change (more than 5°C or 10°F), because such changes alone impact pH measurements.
     
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  4. XNavyDiver

    XNavyDiver Well-Known Member R2R Supporter

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    RSCP mixes at 12 point something, its right on the black bucket. If you're trying to get it down, switch to something that mixes at lower alk, like the blue bucket. Not sure why a CO2 scrubber wouldn't raise your pH.
     
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  5. Andy G

    Andy G Well-Known Member

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    Me neither, only the 1st two days I can get 8.0, then it drops...
     
  6. Andy G

    Andy G Well-Known Member

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    I was guessing it could be the salt. But then why the Ph did low. Should I worry if the Calcium is 450?
     
  7. Andy G

    Andy G Well-Known Member

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    Will do, thanks a lot.
     
  8. John Gemmel

    John Gemmel Well-Known Member

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    450 is good on calcium I would say.. following
     
  9. XNavyDiver

    XNavyDiver Well-Known Member R2R Supporter

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    Is it a new set up? I had the same issue, high alk, and low pH. I switch salt mix and installed a scrubber. pH is now a steady 8.3 and the alk is slowly coming down through WC. Its at about 9.5 now.
     
  10. Andy G

    Andy G Well-Known Member

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    It's fairly new, about 5 months old.

    What salt where you using, and which one are you using now please?

    That might be it.

    Thanks in advance!
     
  11. XNavyDiver

    XNavyDiver Well-Known Member R2R Supporter

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    About the same timeframe as mine. I started it with RSCP like you. I switched to Fritz RPM. The problem was there just wasn't the demand in my tank for all that alk. There wont be for some time yet (I have about 15 sps frags, that's it at the moment), so I switched to a lower alk salt. I will dose when it starts getting used up.
    Its weird about your scrubber though. Is the media out of date? Seems it should have an effect on your pH if everything is in working order.
     
  12. Andy G

    Andy G Well-Known Member

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    If i change the media it goes up to 8.
    But I need to change it every 3 days!
     
  13. rock_lobster

    rock_lobster Well-Known Member R2R Supporter

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    I struggled with this for years and finally found the solution. Naoh but has to be dosed extremely carefully. My pH was 7.7-8 now it's 8-8.3

    IMG_7221.PNG
     
  14. Andy G

    Andy G Well-Known Member

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    Looks great - how did you dose the NAOH?
     
  15. rock_lobster

    rock_lobster Well-Known Member R2R Supporter

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    I run a 24 hour continuous doser so I just add it to my carbonate solution. I mixed .5tsp/50ml and dose 5ml per week in addition to the carbonate.
     
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  16. rock_lobster

    rock_lobster Well-Known Member R2R Supporter

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    That's my pH before adding naoh.

    IMG_7235.PNG
     
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  17. Mindi

    Mindi Well-Known Member

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    Are you using indicating Soda Lime..? if it is exhausted that would explain your problem. I have had exactly the same situation only solved by CO2 scrubber in which 500mls of Medisorb Sodalime is purple in one week. It actually still absorbs enough CO2 even then to hold pH at 8.0 for a second week. Still an expensive solution unfortunately.
     
  18. Andy G

    Andy G Well-Known Member

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    Yes, I'm using color changing soda lime from BRS. It's white on the jar, gets purple in 2-3 days!!!

    At this pace I'll be spending 70usd x month not sustainable.
     
  19. Mindi

    Mindi Well-Known Member

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    yeah exactly...same here..mine takes 6-7 days , it indicates how much CO2 is in the air we are breathing inside. As above mine still works for a while after it goes coloured. I pay 60 aud for 5 litres of medical grade Medisorb and at 500mls a week that is 10 weeks for 60 bucks... nah..
     
  20. Bruce Burnett

    Bruce Burnett Well-Known Member

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    if this is true then it is as Randy stated can only be co2 in the water and more than likely the room. Depending on size of tank and co2 levels in the room it could take 24 hours or longer with windows open to see a significant rise in tank ph. If the levels of co2 are elevated enough then the exchange at the water surface of the tank and sump may exceed what your skimmer with co2 scrubber may be capable of doing. Do Randy's test with water sample outside. Obviously you will need a different ph meter as your Apex is not going outside. Be sure what ever meter you are using use it to test the tank and outside. There are many articles on reef2reef on raising tank ph and if you really need to.
     
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