Low orp

Discussion in 'Reef Chemistry' started by L/B Block, May 19, 2017.

  1. L/B Block

    L/B Block Supporting Member

    Orp is recommended to be in the 300-450 range. Did a water change today and it's coming in at 185 now. Before It was hovering at 220 or so.
    Be concerned, not be concerned? Should I be doing anything-ozone? Which I prefer to avoid just because of exposure reasons.


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  2. Flagg37

    Flagg37 Colorado member

    Out of all the things we measure in our tanks, I think ORP is one of the least important or useful. I wouldn't worry too much about it. ORP and pH are loosely tied together in that usually when your ORP is low your pH is higher and visa versa.
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  3. Coral reefer

    Coral reefer President

    Don't even look at it. I actually don't even know what it means.
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  4. L/B Block

    L/B Block Supporting Member

    Thank you for weighing on a small debate in the house on this.

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  5. L/B Block

    L/B Block Supporting Member

    Thanks. One less thing to worry about

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  6. L/B Block

    L/B Block Supporting Member

    Hey! Wifey doesn't think this settles the debate!

    So... if you set an alarm form when ORP reaches (say) 700, would that be a good trigger to start paying attention to your other water chemistry?

    I agree it is kinda meaningless alone. But my gut says if ORP blows sky high, then something is messed up with the tank. One would hope we'd know that way before ORP went up, but if we are traveling and get an alert - we would call someone to come look at the tank.

    In that narrow purpose, would it be worth leaving in the ORP probe?

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  7. tankguy

    tankguy BOD

    I never heard of it either.
  8. Vhuang168

    Vhuang168 Supporting Member

    ORP is not often measured. While it serves a purpose, it is usually just used to track trends. If it trends up or down rapidly then something is happening in the tank.

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  9. Gablami

    Gablami Supporting Member

    Mine drops after water changes too. And then it trends up with daily fluctuations with pH. When I stir the sand and release a bunch of detritus it drops. That's about all I know about my ORP, but I still like to look at it.

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  10. xcaret

    xcaret Supporting Member

    If you were to run an Ozone unit, I believe you'd need to check ORP otherwise I don't recall a need for that.
    Ozone is used along with skimmers normally and if I recall right, sometimes to make water "crystal clear" by oxidizing some organics
  11. Flagg37

    Flagg37 Colorado member


    I'm not sure if you've read this, but it explains ORP very well and in terms that are easily understood. It is a very complex measurement to fully understand but the article will give you a good base. It's not meant to be a scientific discourse.

    I agree with @Vhuang168 that it is good for tracking trends. With my tank it averages about 270, but like I said, it will vary conversely with the pH swing.
    This is the trend that I expect solely based on what it's done in the past. If it all of a sudden took off to 700 I'd probably check the probe first but it would signal to me that there is something wrong with MY tank. There are other tanks that run much higher; I don't know about 700, but I've heard of 500. Each tank is different and should only be compared with itself. Give it some time, maybe a couple months of watching it and seeing how it reacts to different things.
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  12. L/B Block

    L/B Block Supporting Member

    I'm hoping we'd notice something was off way before 700. :)

    My thinking is this: the probe came with our setup, and as long as we are paying close attention, looking at ORP wouldn't tell us anything we don't already know.

    However, when we are on vacation, and something spikes, it could indicate that our house sitter missed something and we should ask someone to come check. Sounds like that value might be 500.

    Seem reasonable?

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  13. rygh

    rygh Supporting Member

    Mine spikes randomly, usually down but not always, when I do big water changes, change GFO, or add rock.
    But it is very consistent when nothing is touched. Usually 300-350 with a nice daily swing.

    So a < 200, >500 would be a good vacation warning message. I may do that myself.

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  14. L/B Block

    L/B Block Supporting Member

    And with that, the husband conceded defeat and handed me the $1 bill. (Our standard bet.). Now if I can figure out how to get AquaNotes running on my PC to set the alarm.... we have it in our iPhones but keep getting threatening messages that it will sunset!

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  15. Kremis

    Kremis Supporting Member

    never heard of orp in my life. from reading the thread it looks like it doesnt direclty effect corals?
  16. rygh

    rygh Supporting Member

    Correct. It does not.
    And unless you run ozone, you never try to control it or really care about the exact value.
    It is simply an indicator of what is going on in your system.
    Stable is good.
    It does tend to jump suddenly when things die, or when sand bed is suddenly disturbed, like when a powerhead falls, or
    when return pump stops working.
  17. xcaret

    xcaret Supporting Member

    You should not worry about ORP at all and just enjoy you vacation.
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