ORP Observations - A gross novel use

[Biologic]

What I find one of the most interesting subjects in this hobby is ORP. It is almost kind of a pointless novelty -- but can it be made useful grossly? Can I get ball park ideas how it can help me?

I do not see the connection of "a lower ORP relates to dirty water". In fact it's the opposite for my instrument 2016 Neptune Apex. Like many, I see ORP pushed down with water changes. I often use this metric to figure out when exactly was the last time I did a water change, which at this point seems to be its only usefulness to me.

Strong reducers like Vitamin C show significant impacts to ORP as seen on my graph. My saltwater has Vitamin C and Amino acids added to the mix. Which can take the ORP from 250 mV to "plunge spike" 180 mV to a "recovery" 205 mV. This value gradually increases over 6 days to 250 mV. Same with my new additive AquaVitro Fuel has aminos, trace elements, and vitamin C. (not that vitamins matter in aquaculture)

Trying apply some type of use --

You can see this clearly with food and additives, a significant "plunge" and "recovery" but stabilizing close to what it was previously before the addition of the product. I am adding AquaVitro Fuel for the first time this week. It has trace elements and amino acids and vitamin C and B vitamins. I don't really care about the vitamins, but trace is important for me. It's nice to know when was the last time I dosed in this product. Again, a small usefulness of ORP. However, I know that trace elements like Iron are rapidly depleted in the aquarium, so can this grossly give a ball park idea on trace concentration in the tank water?

Measuring brand new fresh saltwater mix that's 24 hours old the ORP concentration is at 140 mV. Assuming that this saltwater has all the trace elements it's advertised to have, and if it's included ICP-OES is correct, this saltwater is "ideal" in terms of what the manufacture sees our saltwater to be. It's a high quality salt.

Going back through logs of data seeing before I started adding this products. On a 10% average weekly water change, I average around 225 to 235 mV for tank water weekly.

What if I can determine how the tank is overall performing (GROSSLY) based on the mV value for trace elements present in my tank water?

 

[Randy Holmes-Farley Verified Community Expert]

What I find one of the most interesting subjects in this hobby is ORP. It is almost kind of a pointless novelty -- but can it be made useful grossly? Can I get ball park ideas how it can help me?

I do not see the connection of "a lower ORP relates to dirty water". In fact it's the opposite for my instrument 2016 Neptune Apex. Like many, I see ORP pushed down with water changes. I often use this metric to figure out when exactly was the last time I did a water change, which at this point seems to be its only usefulness to me.

I too have never agreed with that assertion. It makes no sense. Perfectly "clean" new salt water as low ORP due simply to the lower oxidation state of the ingredients, not because it is dirty.

ORP and the Reef Aquarium - Reefkeeping.com

ORP and water quality

Many aquarists have been lead to believe that ORP is a measure of water quality or purity. Manufacturers selling ozonizers and other oxidizers (like permanganate) have been especially keen to present that idea. But is it really true? Is a higher redox indicative of "purer water" even when that redox is manipulated artificially by adding strong oxidizers? Or is such an addition analogous to an air freshener that masks odors? I don't know the answer, but I think that aquarists should ask the question, and hope to hear useful answers before adding such materials to their aquaria.

Obviously, one can decrease the yellowing of water fairly quickly with oxidizers. It turns out, however, than many organic functional groups that provide color are just the ones that are readily oxidized. It is a common trick for organic chemists that need organic compounds to lack colored impurities to add an oxidizer that "kills off" the color in certain impurities, but leaves nearly all of the primary organic compounds behind. I've done it myself when making dyes for photographic film. You don't want the film to be yellow, so an oxidizer is added to the dye, let it oxidize the color away, and then use the unaffected dye in the film.

Of course, that decolorizing itself can be viewed as beneficial, but it is not necessarily indicative of the load of organics that have been removed from the solution. It is also not necessarily indicative of an improvement for tank inhabitants. The oxidizer did something to the organics. Maybe they are less toxic in the oxidized forms. Or maybe they are more toxic. Or perhaps they are not toxic regardless of the form. Maybe they are more readily metabolized by bacteria. Is that a benefit? The point is that assuming that such a treatment is of significant benefit to the aquarium may be in error.

If an oxidizer is added and ORP goes up in 30 seconds, is the water purer? Not likely. More likely, that addition shifted many of the redox species to their more oxidizing forms. Is that beneficial? Maybe. Is it detrimental? Maybe. For example, the bioavailability of certain metals may depend on the form that those metals take. Is increasing bioavailability of them desirable? It all depends on the details. Details that are simply not known for aquaria.

Perhaps continual use of ozone does help clear some organics from the water, and there is a long term benefit that may or may not be related to actual ORP readings that one gets from an aquarium. Is there data showing that to be the case, and then coupling that with some objective measure of benefit to the aquarium? Does that outweigh the potential concerns about the toxicity of reactive oxidants in aquaria? Again, I do not know the answer. Only careful studies with clear endpoints can give such an answer.

 

[Biologic]

It is a common trick for organic chemists that need organic compounds to lack colored impurities to add an oxidizer that "kills off" the color in certain impurities, but leaves nearly all of the primary organic compounds behind.

Ozone can easily attack alkenes, unstable bonds, and cleave them and breaks them into smaller components, and yes the smaller compounds can still need to be further reduced, and then dealt with the tank's biology. So yeah, they aren't GONE. lol. I'm not sure if the risk is worth the rewards with Ozone, and I am unsure about what happens with trace elements, and their oxidation states. Risk of overdose. Risk of headaches. But yeah different subject totally from my original post.

What do you think of it acting in the reverse "water that lacks trace elements" has a higher ORP, so therefore one can grossly track the need to exchange the water to add in trace elements from a water change?

If its use is little to none, why track it at all? At this point, nobody really has any good use for it, other than a very small minority of ozone users. Yet, it's in many aquarium controllers. If I was Neptune systems, I'd drop it from the platform and offer it as an expansion module only.

 

[Randy Holmes-Farley Verified Community Expert]

Ozone can easily attack alkenes, unstable bonds, and cleave them and breaks them into smaller components, and yes the smaller compounds can still need to be further reduced, and then dealt with the tank's biology. So yeah, they aren't GONE. lol. I'm not sure if the risk is worth the rewards with Ozone, and I am unsure about what happens with trace elements, and their oxidation states. Risk of overdose. Risk of headaches. But yeah different subject totally from my original post.

What do you think of it acting in the reverse "water that lacks trace elements" has a higher ORP, so therefore one can grossly track the need to exchange the water to add in trace elements from a water change?

If its use is little to none, why track it at all? At this point, nobody really has any good use for it, other than a very small minority of ozone users. Yet, it's in many aquarium controllers. If I was Neptune systems, I'd drop it from the platform and offer it as an expansion module only.

Too many or too few trace elements says nothing about whether ORP is high or low or “average”. It depends entirely on the oxidation state of those trace elements.

 

[gbru316]

Do you aerate your water change water? Not just stir with pump -- aerate with an air pump/stone. Lower oxygenation is what I've always attributed the low ORP value associated with "new" water to. Though admittedly I've no scientific basis on which to pin this hypothesis.

I suppose I could do a test when I've got the time.

 

[Randy Holmes-Farley Verified Community Expert]

Do you aerate your water change water? Not just stir with pump -- aerate with an air pump/stone. Lower oxygenation is what I've always attributed the low ORP value associated with "new" water to. Though admittedly I've no scientific basis on which to pin this hypothesis.

I suppose I could do a test when I've got the time.

If you aerate it long enough, the ORP will rise as the trace elements are oxidized, but they can become less soluble and precipitate out, which presumably is why they use the ingredients they do. Ferrous iron (Fe++, low ORP), for example is much more soluble than is ferric iron (Fe+++, higher ORP).

FWIW, ORP itself is not a measure of the O2 present.

 

[gbru316]

FWIW, ORP itself is not a measure of the O2 present.

Right, I didn't intend to make a direct correlation between ORP and O2 saturation. Just that higher O2 presence might have an impact -- albeit indirect -- on ORP.

Haven't finished coffee yet, probably could have worded it better.

 

[Biologic]

Do you aerate your water change water? Not just stir with pump -- aerate with an air pump/stone. Lower oxygenation is what I've always attributed the low ORP value associated with "new" water to. Though admittedly I've no scientific basis on which to pin this hypothesis.

I suppose I could do a test when I've got the time.

absolutely I aerate. Outside. Since pH is effected by indoor atmospheric CO2. I paid good money for my salt. In fact I use maxjet pump with venturi and a maxi jet flow pump set up before I even add salt in. Then mix for a while with the pump and aeration.

low oxidation value is due to what species of iron and the higher iodine found in fresh mix. I read the RHF articles.

 

[Biologic]

Too many or too few trace elements says nothing about whether ORP is high or low or “average”. It depends entirely on the oxidation state of those trace elements.

the spike downwards and then rebounds mean they are changing oxidative states, but not necessarily consumed in biological reactions. Right?

 

[Randy Holmes-Farley Verified Community Expert]

the spike downwards and then rebounds mean they are changing oxidative states, but not necessarily consumed in biological reactions. Right?

Yes, that would be my expectation. Ferrous iron, for example, would be expected to oxidize in normal seawater.

 

[OfficeReefer]

I have long been wondering this myself. It's been something that is discussed in similar hobbies, such as those for pools. I consider ORP much like the farting noises that can be programmed into a Tesla. Interesting to observe and might be whimsical but doesn't really add a lot of value. Maybe one might have usefulness to this, perhaps in holding or quarantine tanks?

Would it not also be useful in reactors and systems where one regularly cleans out or refreshes tanks?

 

[killer2001]

I'm still new to the hobby but I dumped a capful of Seachem Prime into my 45gal with one black molly (mid-cycle) and I watched the ORP go from mid-200's to about 180 and the molly rushed to the surface gulping for air. Luckily, I recognized it right away and turned my skimmer on to increase oxygen in the water.

 

[Randy Holmes-Farley Verified Community Expert]

I'm still new to the hobby but I dumped a capful of Seachem Prime into my 45gal with one black molly (mid-cycle) and I watched the ORP go from mid-200's to about 180 and the molly rushed to the surface gulping for air. Luckily, I recognized it right away and turned my skimmer on to increase oxygen in the water.

Well, it’s not necessarily because O2 dropped, but just because the ingredients are low ORP chemicals. Vitamin C does the same thing.

 

[Randy Holmes-Farley Verified Community Expert]

Would it not also be useful in reactors and systems where one regularly cleans out or refreshes tanks?

What sort of reactor?

 

[billyocean]

I don't fully understand it all myself. However, I do see my corals health. If my orp (apex) is high 200s they don't look as happy when it's 350ish to 400s. The quick fluctuations don't do anything that I've seen but when it's consistently low they don't look as good. I use it as more of a barometer of anything I should be worried about but have no idea why it matters..lol.

 

[Biologic]

I don't fully understand it all myself. However, I do see my corals health. If my orp (apex) is high 200s they don't look as happy when it's 350ish to 400s. The quick fluctuations don't do anything that I've seen but when it's consistently low they don't look as good. I use it as more of a barometer of anything I should be worried about but have no idea why it matters..lol.

interesting observation. It’s totally subjective of what looks good and is that your mind’s influence of what you seek, but interesting.

I don’t think I could ever achieve that value with me performing 10% weekly water changes.

 

[OfficeReefer]

What sort of reactor?

I'm thinking of an SWGC

 

[billyocean]

interesting observation. It’s totally subjective of what looks good and is that your mind’s influence of what you seek, but interesting.

I don’t think I could ever achieve that value with me performing 10% weekly water changes.

The orp goes down steadily albeit slight with time between water changes. I usually do 20 gallons every week and a half give or take. So in turn, yes, it is in correlation with water changes. Water change day it drops significantly for a day but this may be due to the fact that my sump is off for an hour or so?

 

[Randy Holmes-Farley Verified Community Expert]

I don't fully understand it all myself. However, I do see my corals health. If my orp (apex) is high 200s they don't look as happy when it's 350ish to 400s. The quick fluctuations don't do anything that I've seen but when it's consistently low they don't look as good. I use it as more of a barometer of anything I should be worried about but have no idea why it matters..lol.

I agree that so many things change ORP or change because ORP changes that it makes it very hard to understand which effects cause specific observations.

 

[Randy Holmes-Farley Verified Community Expert]

The orp goes down steadily albeit slight with time between water changes. I usually do 20 gallons every week and a half give or take. So in turn, yes, it is in correlation with water changes. Water change day it drops significantly for a day but this may be due to the fact that my sump is off for an hour or so?

I think it is because new salt water has trace elements in a low ORP state.

Try measuring the ORP of the new salt water before the change. It is likely quite low.