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Measuring ORP, how to interpret?

Discussion in 'General Plant Topics' started by Gilles, Jul 30, 2009.

  1. Gilles

    Gilles Lifetime Members
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    Yesterday i installed my ORP sensor, and it was reading 172mv. Today it was reading 163mv. I've read on the internet various values, ranging from "You should have 300mv to 450mv for freshwater" and also "You should have 250mv".

    I've read all the articles i can but i can't seem to find what ORP does, how to "improve" it etc... Can somebody give some explanation about this?

    Thank you,
    Gilles
     
  2. wilsar

    wilsar Prolific Poster

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  3. Gilles

    Gilles Lifetime Members
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    Hi Wilsar, that value is specific for saltwater.. But thans for the link!
     
  4. Tom Barr

    Tom Barr Founder
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    I think if the tank was growing really well, the ORP would be pretty high in your tank.

    I rarely use ORP for anything in the water column, the only reason it might be used is for Marine systems and then mostly for using and controlling Ozone gas.

    For freshwater, particularly planted tanks, it has a very interesting use.
    Sediments.

    I believe you use mostly plain sand however.
    The ORP is typically pretty close to that of the water column, it will get slightly lower as you insert the probes deeper if the sediment has had some time to accumulate organic matter, detritus etc.

    ADA AS, mineralized mud/soil, worm castings and various other organic loading, N and P enriched sediemtns will have lower ORP.

    You can take the tip and insert it into sediment and then wait a few days, then take the measurement.

    If you just push the ORP probe, then you are bring in a lot of O2 by inserting it, so it needs time to readjust to the low O2/ORP that was there before you disturbed things.

    You can slowly push the ORP probe down every cm and take the readings doing this type of method. You also can measure the differences between plant root regions and those without any plants during the day and also during the might.

    Many test you can do, but most planted hobbyist have never even considered using them. It is the main parameter used in testing and monitoring sediment.
    Many hobbyists like to claim to be experts on sediment and have virtually no understanding of organic carbon and ORP. So basically they know nothing of the relationships in sediments of wetland plants.

    They may know that sediment A grows plants better than sediment B.
    But not much more..........


    You can also do pot experiments and use the different sediments and use ORP to compare.

    Many different treatments and things we could do.

    Regards,
    Tom Barr
     
  5. Biollante

    Biollante Lifetime Charter Member
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    Hi Gilles,

    I also would expect a higher sensor reading. In fact, I would anticipate, in a plant growing, fish friendly environment, more like 400mv, though I also would caution against getting hung up on a number.

    ORP sensor readings are indicators, in my unworthy opinion, people (you know who you are, bright-adapted eyes, brains, opposable thumbs) tend to over analyze ORP numbers.

    Having said that I believe ORP numbers may allow us to understand the fundamental balancing act of our closed little biological systems.

    As you are, learning and experimenting with your ORP meter, a couple of things to keep in mind:
    1. Your aquarium (or for that matter; nature) is never in balance, it is always seeking balance. This is where I think we confuse ourselves.
    2. The best electron acceptor is oxygen. The reason I would expect a higher reading.
    3. After O2 is nitrogen.
    4. Then manganese, iron, sulfate, carbon dioxide.

    Once you start into the substrate the iron is the way we track phosphate availability and uptake, for instance.

    This is a presentation I like that gives, I think, a good overview. http://kearney.ucdavis.edu/Undergrad_Fellowship_Reports/ChangKearney_Presentation.pdf

    I gather these folks are selling something but seem to be good Redox information. How Aquarium Redox Balance, Potential, & Reduction relates to aquatic health

    If you are interested, I have more to say.:eek:

    Biollante
     
  6. Gilles

    Gilles Lifetime Members
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    Please do say more, i want to learn more about this. I have it currently hanging in my water column (in my sump to be exact, first compartment right where the tank water flows in). My sump is by my own design i will post some pics of it explaining the reasons and design behind it. I'm almost sure you will be suprised ;)

    Anyway; as i've read on most sites. ORP is also an indicator of the bacteria at work. Right now i have reduction in my tank. I could use some more oxidation if i wanted to help the conversion of any ammonia (NH3) to nitrites (NO2–) and nitrates (NO3–).

    But i wonder; can i help my plants by adding oxygen for a short time? I know that oxygen removes CO2, but if i can boost my oxygen levels for e.g. 2 days which results in a better ORP maybe my plants kick off also..? I do have a computer controlled PH meter, so the PH will be stable at the rate i've set it to (pH 6.2 with KH 3).

    I dose PPMD regularly containing K2SO4, Fe2 and Epsom salt for Mg.
     
  7. Biollante

    Biollante Lifetime Charter Member
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    ORP Meter

    Hi Gilles.

    First, I want to give a disclaimer beyond my normal disclaimer, ORP (Oxygen Reduction Potential) or Redox (Reduction-Oxidation) reaction, can get complicated fast and it is incredibly easy to jump to the wrong conclusion and in a big hurry. I am not an expert, nor have I played one on TV. I am someone who has been fumbling around with these concepts for a while. I think I have some practical aspects down. Then see my disclaimer!

    Second, I think that a decent, calibrated ORP meter is one of the best investments a serious aquatic hobbyist can make.

    Third, keep notes. This is our opportunity to do some (I hope, good) basic science and help spot trends.;)

    Forth, most of the readily available information about Redox comes from fields other than aquarium keeping. More on this in a future post.

    Fifth, use common sense; don’t let a particular reading overwhelm you. This actually goes for any testing.

    Sixth, when in doubt, do a major water change.:) Hey, it won’t hurt and it will give you the feeling you’ve done something.

    I actually started using ORP meters to understand and manage filtration in an aquaculture (high bio-load) environment. After a while ORP is like any other tool, we hope to develop a ‘feel’ for what the various readings mean. We spot trends.

    Now on to your tank.

    You mentioned a KH of 3 I’ll assume that is 3dKH with a pH of 6.2, which seems low. Do you know how many degrees GH? Do you use a drop checker(s)?

    Are you happy? Are you happy with the condition of your tank?

    How does it smell?

    How are the critters doing? Are they happy? Do they look stressed? Do they eat well? Are they breeding?

    Are the plants happy? Are the growing? Do they look good?

    The location, in a sump, may explain the readings. I would like to see a diagram or picture of the sump, as I said we don’t want to over-react to these readings .

    I would like to go through this with you if you are willing. To be honest, I have formed an opinion, but I would rather keep it to myself and go through ‘the process’ with you. I think you have a very good attitude.

    If you get frustrated with me, or think, I’m being obnoxious (what part of evil plant monster don’t you get:eek: :confused: ), say so and I will back off and give you my opinion.

    Biollante
     
  8. Gilles

    Gilles Lifetime Members
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    Hi Biollante, on to your questions:

    Good, i only submerged my ORP meter for 2 days now, i've heared it is a decent one and i also heared i have to wait for up to 2 weeks in order to stabilize.

    I have been using drop checkers for over 4 years. I never used strips :p
    The GH is about 4-5. This is because i want to grow toninas. That is why i have these parameters.

    Besides some serious algue issues (from which the cause can be found in overdosing EI (with TMG which had Nitrates & phosphates).. :p Yes i am happy. The algue is on its return and i feel my tank is finally maturing. Fish are breeding, eating and doing exceptionally well. My tank does not smell at all. The plants look happy although there are some issues i have to adress (like wrong plant groups together).

    I am more then happy to discuss my diagram and setup of my current tank with you. As a disclaimer of my own i must allready tell you that my new tank (which is in preperation) will not have a sump anymore. it will run on canister filters.

    Expect a big post this weekend in my tank log about my current conditions. I hope we can discuss the ORP in this thread, since it is such an (in my opinion) important aspect of the hobby.

    By the way; here is the quote on the aquariumcomputer.com/forum part:
     
  9. Biollante

    Biollante Lifetime Charter Member
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    200mV, 250mV, 400mV ??

    Hi Gillis,

    I agree with Aqua_digital ORP, what should you target? - ProfiLux Support Forum, at least the patience, take time and follow it over time.

    That is why I really wanted to know, still want to know the condition of your tank. What your expectations are. ORP numbers aren't magic. :cool:

    The fact that you are happy goes along way to convince me you really don't have a problem.:)

    I suppose on the note of the 400Mv reading, that is arbitrary and for our purposes as aquarium keepers I suspect anything over 250-300, okay I'll accept 200mV or whatever number someone chooses, likely doesn't tell us anything, besides, you have good water.:cool:

    Though I think in a mature well maintained freshwater tank numbers around 400Mv are not unreasonable. In the saltwater community 250 with ozone is reasonable, many reef-keepers are routinely targeting 400mV or even 450mV. I don't have any real experience with reef systems, I don't know how realistic that target is, I suspect it is pushing the envelop.

    That is why I think there are more interesting places to but the probe than in the water column, your sump may be a good start.

    More later.

    Biollante
     
  10. Gerryd

    Gerryd Plant Guru Team
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    Hi Gilles,

    Tom and others have shown that nutrient overload in and of itself does not cause algae.

    I would say your algal and plant growth issues are more likely c02 related than anything else but that is without knowing anything about your tank. However c02 is much misunderstood in terms of it's application and use in growing aquatic plants.

    I would be interested in learning more details about your setup, progress, etc and in knowing what algae issues you do have?

    It could well be a matter of too much light and not enough c02 for the light levels provided. This could cause all sorts of issues regardless of dosing EI..
     
  11. Gilles

    Gilles Lifetime Members
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    Hi Gerryd, the algue issues i HAD (!! hehe) (search for it here) are long gone since i reduced my lights to 60% (6x54w T5HO) , did some massive water changes and just looked at my filter setup. I now have white cloth and seachem purigen and seachem matrix in my sump. As you can say.. it is almost empty and it seems to work really really well for me.

    The only issue i have right now is some minor staghorn algue (or Cladophora, don't know yet) issues and some green hair algue. In case of the latter.. nothing a good running aquarium can't fix so i'll just wait for it to vanish ;)

    By the way; i've also noticed that some of my plants have roots are growing upwards (e.g. out of the substrate which is pure sand 0.5-1mm) with some ADA root sticks :p
     
  12. pepetj

    pepetj Lifetime Members
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    Oxydation/Reduction Potential is an interesting but mostly overlooked water parameter. Most info in the web suggest readings of +400mv to be harmful; for quite some time positive values were/still are considered healthy (+250 to +300mV), but that seems to be challenged by a proposal that a reduced environment is indeed better (-250 to -350mV).

    I suggest you read Carl Strohmeyer's article "The Redox Potential (ORP) in Aquarium (& Ponds); how it relates to proper aquatic health". He runs a business but seems quite honest and open as he frequently corrects himself as he gets new data.


    Pepetj
    Santo Domingo
     
  13. Biollante

    Biollante Lifetime Charter Member
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    I suggest you read Carl Strohmeyer's article "The Redox Potential (ORP) in Aquarium (& Ponds); how it relates to proper aquatic health". He runs a business but seems quite honest and open as he frequently corrects himself as he gets new data.


    Pepetj
    Santo Domingo[/QUOTE]

    I think I referenced this in an earlier post by Carl Sttrohmeyer in an earlier post. How Aquarium Redox Balance, Potential, & Reduction relates to aquatic health

    He is selling something, Wonder Shells, I don't know anything about them but I do like the explanations in his article.

    Just me, but anything under 250mV in the water column and I would be doing massive water changes. I still like closer to 400mV in the water column.

    Biollante
     
  14. Tom Barr

    Tom Barr Founder
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    -250 mV to -350mV is deadly to aquatic plants, fish, shrimp, you name it.........it's devoid of any O2.

    A much better reference about Redox and aquatic plants:

    Reddy and DeLaune, 2008: Biogeochemistry of Wetlands.

    This is specific and without a doubt, one of the top text anywhere on the topic of plants and Redox.

    Redox of the water column changes and varied widely depending on the time of day, location, depth etc.

    You are chasing things by only looking at one reading per day.

    Here is a good run down on Redox and wetland soils:

    Wetland Soils (Wetland Biogeochemistry)
    This is from a university, not a hobbyists trying to sell something.

    Specific papers:

    Wetland Biogeochemistry Laboratory

    Oxidation of the Root Zone by Aquatic Plants Growing in Gravel-Nutrient Solution Culture -- Steinberg and Coonrod 23 (5): 907 -- Journal of Environmental Quality

    Regards,
    tom Barr
     
  15. Gilles

    Gilles Lifetime Members
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    Yesterday after a omsosis water change; 150mV. I added an airstone after the lights went off, just to see if i could bounce the value up and if it will affect pearling in my tank. Off course; now the lights are on the airstone is removed. The redox reading was 242mV this morning. Lets see how that evolves during the day. Thanks everybody for the reads, i'll have to find some time to read it all..
     
  16. Tom Barr

    Tom Barr Founder
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    I think you could measure O2 easier and find better data correlation with research than Redox.

    The O2 will mirror the Redox pretty well I'd predict.

    Say this morning, the O2 was 6ppm, it might rise to 8ppm after 4-7 hours of the lights on, then drop.

    You can correlate this with Redox once you get a measure for O2.

    Marine aquarist use a stronger oxidizer than O2. They use O3.
    We use a bio produced O2 oxidizer which will change throughout the day cycle diurnally.

    So the Redox should as well, this occurs also in the sediment, but to a lesser degree around roots dependign on growth rates(same dependence on growths in the water column and O2 production).

    So higher growth rates should correlate with high peak Redox levels. If you get 12-14ppm of O2(at say 28C) in very very productive systems, plants, algae etc starts dying off and you will get a massive decline, but this is very rare in our tanks, I've never seen it yet, likely because we do not have enough light to do it.

    Regards,
    Tom Barr
     
  17. Biollante

    Biollante Lifetime Charter Member
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    Ro/di

    Hi Gillis,

    I would expect a lower ORP reading in water directly added from reverse osmosis (RO) filter even more so with deionized (DI) water.

    I may have misunderstood your post regarding the use of RO water, if I did my apologies in advance.

    Being a plant, my opinions are always humble. :eek:

    However, it is my opinion that using RO or DI water directly into aquaria is a bad idea. RO/DI water should be ‘reconstituted’ in some means, usually by the addition of electrolytes and oxygenation prior to adding to the aquarium or for that matter use by plants, people or pets.

    Though this isn’t a scientific paper, associated with a major university, I think it may help give some insight to the use of RO and/or DI water. Let's talk RO water. :: FishGeeks :: Tropical fish - Marine Fish - Aquarium Fish - Pond Fish - Aquatic Plants

    I think I have some better citations elsewhere.:confused:

    Biollante
     
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