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Thread: Freshwater ORP over 500?

  1. #1
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    Freshwater ORP over 500?

    Hey there, I am using lab-grade ORP probe (I believe it's Pinpoint Marine off the top of my head) in my 48 gal freshwater planted tank. I do have an ozone reactor, but it's never on (I'm not entirely sure it works, anyway, it never seems to raise the ORP when it kicks on, but It's not apparently hurting anything) BUT I was wondering why my ORP is over 500 mV without any Ozone being used at all? Is this problematic? The probe seems fine and has been in the sump for a couple of months. It's clean. Tank is grounded.

    I have recently set the pH controller to stay on 24/7 instead of just during the photoperiod. This is the only factor, that I can think of, that has changed. Everything I have read indicates not to let your ORP rise past 400, and certainly not 450. This advice was in the context of SW husbandry, however.


  2. #2
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    I just did a water change and it's showing an ORP of 596! No one can offer any insight?

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    First, are you using ozone? If so, stop until you get a stable baseline.

    Otherwise, I have the opposite problem. My ORP won't rise above 320. I'm guessing the accuracy of the probe, original calibration by Apex, isn't very important as long as the precision is there by paying attention to the fluctuations from your baseline. I have coral growing at 310-320 daily with oscillations counter to my pH of 8.05-8.25. Are you seeing oscillations relative to your pH? Is it dropping after feeding putting additives in the water? If you are overly concerned do a 20% RO water change and see if it makes a difference in the reading. If not, just track against your baseline.

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    Also check to see what is close to your ORP cable in case you are getting interfence. Do you have the excess looped to reduce antenna effect?

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    I am not using ozone since the ORP is over 450. It has been off for a week. I did a massive water change and the ORP dropped as expected. It has been several days now and it is 422 as of a couple of hours ago. This is because the pH rose since I coincidentally ran out of CO2.

    I turned on the Ozone to see what would happen (I only have a few otocinclus in there) and it has gone from 422 to 429 in about an hour. I don't know how Ozone really acts with freshwater, and no one else does either. I shelled out the dough because I heard so many great things about it but I feel like I'm wandering in the dark lol.

    It was looking more normal during the cycling process (I'm using ADA aquasoil if that has any relevence, full of tannins, ammonia etc.)

    I do see oscillations with pH fluctions as you would expect. Currently pH is 7.28. I am using an Ozotech 220 mg/Hr generator powered by an Alita vacuum pump attached to an Ozotech automatic air drier attached to silica chamber. The ozone is fed into the following Ozone reactor, which is powered by an Vortech m1:

    http://www.atomic-reactor.co.uk/prod...r-600-2000-lt/

    I would NEVER recommend that reactor to anyone. I really wanted the Reef Octopus reactor, but it was one inch too tall for my stand.

    Filbie, I have the tank grounded and I have all of the probe cords looped to be tidy, but I have never heard of the antenna effect. I will investigate that! I will double check the cable, too. It's totally possible I pulled the loop loose working in my sump. Sump is pretty loaded.

    To be honest, the only reason I have a sump is to use this ozone reactor. My heart is sort of set on making this work on what is supposed to be my "Dream tank", but if I can't make it work then I might as well get rid of the sump setup altogether. It out gasses so much co2 I am going through ten pounds a month and it's only a 50 gallon tank. I could live with looking at the probes and co2 reactor in the main tank, but I would rather rather make this ozone setup work and keep the sump.

    I had some ORP calibration solution, but when I tried to calibrate it (like three times) it fails each time. I guess that's because I'm not mixing my own two-point solutions. The guys at BRS said you didn't really need to calibrate it, anyway.

  6. #6
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    Yeah, it has been two hours since I turned on my ozone. 220 mg/hr (highest setting) used with air drier, good quality air pump, reactor powered by Vortech m1 on lowest flow setting for longer contact time. I feel like ORP should have risen more than 8 mV in two hours. Why bother? Aug 12, 2016 05-27-06.jpg

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    I switched out the probes and now ORP is reading around 150 W/O O3. Now to just figure out how to make my reactor... react.

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    old stuff, but here is some data of my ORP in freshwater. I'm controlling my pH between 7 and 7.2 during the night by pH controlled CO2 injection.
    You can see that pH and ORP are inversely correlated (or is it electric noise when CO2 injector comes on?).

    Anyhow, I'm not sure I understand the relation. My thinking was that when I inject CO2, there is a drop increase in CO2 over O2 int eh tank, pH drops as expected, but why does ORP climb? I would have thought oxidation potential is actually reduced with increased CO2.

    Screen Shot 2018-04-12 at 1.06.35 PM.jpg

  9. #9
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    It's because ORP is inversely related to pH

    ORP and the Reef Aquarium by Randy Holmes-Farley
    http://reefkeeping.com/issues/2003-1...ture/index.php

    From Randy's article:

    "What about pH? pH can impact the ORP readings in aquaria. Often, ORP goes down as pH rises. A typical aquarium ORP reading will change on the order of 59 mv/pH unit. The easiest way to understand this is to simply think of pH as a measure of hydrogen ions (H+) in solution, and to think of H+ as being on the side of the oxidizers. In reality, H+ doesn't usually oxidize things itself (though it can), but more typically it can hype up other oxidizers, like oxygen, making them much more potent. So during the course of a 24-hour day in a reef aquarium, ORP will vary as pH and O2 also vary."



    You might be an engineer if...You have no life and can prove it mathematically.

  10. #10
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    oh, great, thanks for posting this explanation.

  11. #11
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    Hi,
    Also to add that ORP measurement is irrelevant in the water column of a freshwater system. The relevant Oxidation-Reduction reactions occur in the sediment as a result of bacterial activity and is mediated to a large extent by the plants via their roots. It would be more fruitful to stick the probe into the sediment, and even then the data is difficult to interpret. It's much easier to track the rise in pollution in freshwater by looking at conductivity rise throughout the week as this is a much more direct and obvious relationship.

    Cheers,

  12. #12
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    Got conductivity probe in there as well on a PM2 module. Calibrated it with a 447 solution, have the temp probe hook to the PM2 module (I did a factor of 2.0 TC for now, but not sure what I should have done for fresh water, will play with it over time after having accumulated some data).

    Pretty steady for now (does'nt look that way because of the scale but it's pretty flat if you zoom out),


    Screen Shot 2018-04-13 at 1.24.47 PM.jpg

  13. #13
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    Quote Originally Posted by Morecowwbell View Post
    Got conductivity probe in there as well on a PM2 module. Calibrated it with a 447 solution, have the temp probe hook to the PM2 module (I did a factor of 2.0 TC for now, but not sure what I should have done for fresh water, will play with it over time after having accumulated some data).

    Pretty steady for now (does'nt look that way because of the scale but it's pretty flat if you zoom out),


    Screen Shot 2018-04-13 at 1.24.47 PM.jpg
    I believe you want something in the 0.1 to 0.3 range for freshwater, but I am not 100%. I'm not certain if the temp compensation is based on full scale value or based on ppt. It's pretty easy to check though. Heat the tank up a degree higher than normal and see if the reading stays relatively steady.

    You might be an engineer if...You have no life and can prove it mathematically.

  14. #14
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    yep, couldn't find anywhere online info on TC for freshwater tank and the apex system, so I'll keep it that way for this week to see how stable it is (with water change and dosing fertz, etc).

    and next week I'll try playing with the temp in a cycle fashion (like the ph test I did up above).

    I'll report back what I get for Temp Compensation (probably in a new thread with a proper title to that specific topic.)

  15. #15
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    Hi,
    As with ORP there is no target value or range. The conductivity will vary depending on, for example, whether you use tap water or an RO/tap mix. Adding anything to the water, such as food, nutrients etc. will immediately increase the reading. As fish and plant waste accumulate this will also raise the conductivity, however, as soon as you clean the tank the conductivity will fall, so it's more important to study the trend for your particular tank. In fact it would be very suspicious if the reading stayed flat during the entire week.

    Cheers,

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