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Thread: ORP Baseline

  1. #1
    Oyagoi yerrag's Avatar
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    ORP Baseline

    I've read one or two posts that ORP levels below 200 are not healthy, from 200-300 as relatively clean, and from 300-400 as very clean. But having also read other posts on the matter, this is just a rule of thumb and not set in stone. For one, those values are probably based off a colder temperate climate, and are likely inapplicable to the warm tropical climate, as is one where I am located.

    Having no idea as to what is a good ORP level for me to use as basis. and no ORP vs. temperature chart to work, I thought if I could devise a way to give me assurance that my pond's ORP is ok. This is where I am: Using a newly bought HM Digital ORP 200 which I got from Amazon (no reviews yet) but at around $80 plus around $20 for the storage solution and a calibration pack. I had them calibrated. Next thing was to take values of my water parameters : TDS - absolute (122), relative to mains (48), ammonia (0-ish), nitrite (0-ish), nitrate (10), dkH (3), gH (4), phosphate (5 ppm). Temperature was at 28 degrees C ( or 82 F).

    The night before, I had doubled aeration from 50 to 100 ltr/min, and doubled flow rate from 10,000 ltrs to 20,000 ltrs/hour, lowering the pond fully cycling from 2 hours to 1 hour. My pond has a capacity of 20,000 ltrs, including a 2,000 ltr. filter area. Pond has 4" bottom drain and 2 3" surface skimmers flowing by gravity into the filter area. The filter consists of 5 chambers - sump (non-vertex), brush mechanical filter chamber, two biofiltration chambers, and a UV chamber. UV chamber has been disabled and the use of em-1 microorganisms used in place of it.

    Water return to pump is thru a 3-ft waterfall, a main TPR return to the pond, and thru a small vegetable filter of about 1,000 ltrs.

    10% water change is done twice a week, and a sump and mechanical filter cleaning done once a month. Once a year, the biofilter gets drained and spray-cleaned with pond water.

    Water is clear but has a yellowish tint, and algae only seen at the walls. String algae resides by the 2nd biofilter.

    That said, I got an ORP value of 192 today. Yet I don't know what it really means.

    So I got standing water from the water tank that already has no chlorine, and run it thru a Nikken Optimizer, which aerates water thoroughly. And I got a reading of 212.

    With this reading as my baseline as "clean," I make a determination that my pond water is not too shabby.

    Am I right going this route? Any way I could improve on evaluating my water?

    Thanks!

  2. #2
    Tosai
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    Other than cleanness of water, the PH is the most important factor in determining the ORP reading. One unit change in PH can result in an ORP reading difference of 58. The higher the PH, the lower the ORP reading.

  3. #3
    MCA
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    You may have seen the two files I am attaching. The ORP 101 is the introduction of ORP for koi ponds. The second file is about a far more obscure topic of relative Hydrogen (rH). Pond ORP is influenced by water pH, oxygen levels and other factors. So rH is trying to keep view the measured ORP in the context of the water pH. Lower pH liquids transport electrons more easily. That is why acids are used in batteries instead of base/alkaloid compounds.

    ORP is one snapshot of how well your pond's engine, the filtration and aeration components, are handling the organic load from fish, the food eaten by fish, and any other organic materials that may be in the pond system (algae, potted plants, leaves, nuts....etc.)

    As we know, warmer water holds less DO. As DO drops, the ORP will likely follow. So all other things being equal, someone in a tropical environment may have a slightly harder time with ORP levels that someone in a temperate zone.

    If your pond is consistently measuring 200mV or above, and you have DO at saturate for the temp, don't stress too much. ORP is just one way of looking at how well the pond system is operating. The most important is the health of the koi. If they are not stressed, eatting well, having good growth, and producing excellent skin quality.....you can not ask for more.
    Attached Thumbnails Attached Thumbnails ORP Baseline-orp-101.pdf   ORP Baseline-relative-hydrogen.pdf  
    Koi keeping is not a belief system; it is applied science with a touch of artistry.

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    Oyagoi yerrag's Avatar
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    Quote Originally Posted by whodatkoi View Post
    Other than cleanness of water, the PH is the most important factor in determining the ORP reading. One unit change in PH can result in an ORP reading difference of 58. The higher the PH, the lower the ORP reading.
    And I left out the pH: 7.5

    So if I want to increase the ORP just by playing with pH, I could increase the ORP by allowing the pH to drop to 7 by say, maintaining a lower dkH of 2 instead of 3.

    There appears to be a trade-off between being 'safe' having a large buffer with a high dkH and having a lower ORP. Or having a higher ORP but having a less safe kH reading, less safe being at a point where externally induced change could easily make the pond acidic and unsafe for koi. This calls to mind an article written by Mike Snaden about koi keeping - that if you want to bring out the full potential of a show koi, you have to be willing to be "less safe" by allowing a dkH of 2 and rely on frequent water changes, as opposed to being safe, by maintaining a high dkH of say, 6, which is okay if your aim is to simply care for pond koi.

  5. #5
    Tategoi hewhoisatpeace's Avatar
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    I keep kh of 2-3 with flow through water changes, plus 25% weekly filter cleaning. Works for me, but at 7.8-7.9 pH, I do not currently measure ORP.

  6. #6
    Daihonmei MikeM's Avatar
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    First, ask yourself why you care about ORP.

    IMO, ORP is in itself irrelevant. It only has meaning in the context of other parameters. Understand all of those, and then it can tell you whether you need to do more water changes, reduce stocking, increase aeration, etc.

  7. #7
    Tategoi hewhoisatpeace's Avatar
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    Exactly. The rH measurement seems to be a much better indicator. Maybe one day I'll get bored and test ORP.

  8. #8
    Oyagoi yerrag's Avatar
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    MCA, thank you. The 2nd file is new to me and extremely helpful. Still trying to put it all together. So I'm gonna just think loudly with these points and reason out:

    - The higher the water temperature, the less oxygen is dissolved.
    - The less oxygen is dissolved, the less the ORP.
    - The ORP is maxed out when dissolved oxygen reaches saturation, when the water cannot dissolve any more oxygen.
    - For any given temperature, the maximum ORP can be achieved at the lowest pH deemed safe for koi, which is at a pH of 7?
    - The higher the temperature, the range of pH allowed for healthy pond operation is shorter.
    - Evidence of the danger of high pH and high temperature is the chart of allowed total ammonia in a pH vs. temperature chart
    - A combination of very high temperature and high pH is unhealthy and a low ORP and low rH values are to be expected
    - Using a range of rH deemed safe and healthy for koi is a good aid for the koi keeper
    - The higher temperatures in tropical environment allow less leg room for the koi keeper to be lax with koi upkeep as external changes can easily tip the conditions toward unsafe levels

    Question : If humans can get acclimated to high altitudes by training their circulatory and respiratory to be more efficient in transporting oxygen, would it be not too far-fetched to think that koi can adapt to low DO conditions? What can the koi keeper do to help the koi adapt to such conditions? Is there a koi equivalent of EPO? Will my koi be disqualified from using EPO by the ADKA (Anti-Doping Koi Alliance?)

  9. #9
    MCA
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    If humans can get acclimated to high altitudes by training their circulatory and respiratory to be more efficient in transporting oxygen, would it be not too far-fetched to think that koi can adapt to low DO conditions? What can the koi keeper do to help the koi adapt to such conditions?
    Koi keeping is all about providing an environment where koi can live up to the potential of their genetics. "What can the koi keeper do to help the koi adapt to such conditions?" Give up koi keeping or fix the conditions.

  10. #10
    Oyagoi yerrag's Avatar
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    Quote Originally Posted by MCA View Post
    Koi keeping is all about providing an environment where koi can live up to the potential of their genetics.
    Right.

    "What can the koi keeper do to help the koi adapt to such conditions?" Give up koi keeping or fix the conditions.
    Outside of giving up koi keeping (really), let's talk about fixing the conditions. Understand, I'm talking about aiding the koi in a harsh environment where, short of pouring tons of dollars into recreating cold conditions using pond chillers for the love of your koi, high temperatures exist and low DO levels are the norm. I am not talking about intentionally subjecting koi to crisis conditions and seeing who survives and wins a contest. Just to be sure.

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