Got ORP?

[meschaefer]

When I was drafting the Cyanobacteria Primer, I got to thinking about ORP and have been doing some research into its significance.

An article in the December 2003 issue of Reef Keeping Magazine, by Randy Holmes Farley, entitled ORP and the Reef Aquarium, has been one of the primary places that I have found information on it, and while it makes for a great read, some of it is over my head.

I am primarly intersted in using ORP as one of many measurements of overall water qualtiy. To often, you can see that there is something not right in the system (algae build up, cyanobacteria, etc. etc.) but all of the usual suspects check out. You figure that it is probably a build up of DOC (i.e. time for a water change) but it is ultimately just a guess.

It seems that knowing the tanks ORP and watching the trend (i.e. is it slowly going down, up, level, sudden spike, etc. etc.), you might be able to measure a build up of organics and take corrective action before there is a problem.

Who out there is measuirng orp?; How are you measurieng it (specific equipment)?; and, What do you do with the information that you get?

 

[cali_reef]

ACIII and ACIIIP when I had water in my tanks.

I do pretty much nothing with it, ozone and bigger skimmers were used to adjust the tank.

 

[meschaefer]

ACIII and ACIIIP when I had water in my tanks.

I do pretty much nothing with it, ozone and bigger skimmers were used to adjust the tank.

6am Eastern... up late this morning?

Did you use the Aquacontrolers to control ozone?

Did you ever notice a correlation between decreasing ORP levels and the outbreak of algae?

 

[jhale]

Matt, I measure for it with my controller. I don't try to adjust it in any way, it's just a number I use to judge the overall health of the tank. My tank is usually in the 400's

who's down with ORP this thread has some more ORP info and opinions.

 

[xavier]

Hi,
I?m using a the Milwaukee ORP meter just to control global quality and trend of it. And it really tells me when water quality is decreasing.
I?m keeping it close to 450.
Is just another way to control the parameters and how healthy is the tank

 

[NYPDFrogman]

Milwaukee now, soon to be my aqua controller
my orp is anywhere between 395 and 450 MV
lots of factors contribute to ORP, salinity temperature, dissolved organics

I use just as a measure of water quality
used to use ozone haven't set it up on 450 too many other issues to deal with now

 

[meschaefer]

For anybody that has bee following their ORP for a long time, do you see any correlations between decreasing ORP and algae outbreaks, or overall water quality.

There is an interesting finding in this article, Total Organic Carbon (TOC) and the Reef Aquarium, found in the August issue of Advanced Aqauarist ,

The article states "The TOC content of the author's tank, and ORP readings at the same time points, were measured over the course of a typical week...." and then later on charts TOC and ORP. If you look at the graph you can see that there does not seem to be a correlation between the two. They state that "There is no useful correlation between TOC values and ORP values". They where using some pretty sophisticated lab equipment to take there readings. This would seem to suggest that ORP is not useful in terms of measuring overall water quality.

 

[prattreef]

For anybody that has bee following their ORP for a long time, do you see any corrleations between decreasing ORP and algae outbreaks, or overall water quality.

There is an interesting finding in this article, Total Organic Carbon (TOC) and the Reef Aquarium, found in the August issue of Advanced Aqauarist ,

The article states "The TOC content of the author's tank, and ORP readings at the same time points, were measured over the course of a typical week...." and then later on charts TOC and ORP and finds "There is no useful correlation between TOC values and ORP values". They where using some pretty sophisticated lab equipment to take there readings. This would seem to suggest that ORP is not usefull in terms of measuring overall water quality.

Matt, I can't speak to the findings in that article, but I know who can--Dr. Ken Feldman the author-- and he just happens to be one of the speakers at the next MR frag swap. His topic: "Total Organic Carbon in Reef Aquaria-- The Good, The Bad, The Ugly." You might get some answers there

 

[NYPDFrogman]

I have noticed than when I replace GFO and /or carbon my ORP rises.
I cant say that when it drops I see more micro algae.
I was also on a kick where I was testing dissolved 02
I don't remember the numbers ( I had a log but my desktop crashed waiting for my son to repair it) but I do remember the biggest factor in readings had to do with temp swings, affected disolved o2 and Orp

Matt I kind of get where your going with this as far as algae outbreaks I dont think it will be a simple explantion.

even with PO4 down to .001 and my orp over 400MV I still had cynao
so.....

 

[meschaefer]

Matt, I can't speak to the findings in that article, but I know who can--Dr. Ken Feldman the author-- and he just happens to be one of the speakers at the next MR frag swap. His topic: "Total Organic Carbon in Reef Aquaria-- The Good, The Bad, The Ugly." You might get some answers there

As if I wasn't excited enough to begin with, now I am just down right giddy.

 

[meschaefer]

I have noticed than when I replace GFO and /or carbon my ORP rises.
I cant say that when it drops I see more micro algae.
I was also on a kick where I was testing dissolved 02
I don't remember the numbers ( I had a log but my desktop crashed waiting for my son to repair it) but I do remember the biggest factor in readings had to do with temp swings, affected disolved o2 and Orp

Matt I kind of get where your going with this as far as algae outbreaks I dont think it will be a simple explantion.

even with PO4 down to .001 and my orp over 400MV I still had cynao
so.....

I am kind of interested in using it as a early warning system.

When you GFO/carbon is getting near exhausted do you see a drop in ORP?

 

[jackson6745]

even with PO4 down to .001 and my orp over 400MV I still had cynao
so.....

Frank, where did the cyano grow?

Ozone is the one thing I never experimented with in my reefs. Not sure why

 

[NYPDFrogman]

I am kind of interested in using it as a early warning system.

When you GFO/carbon is getting near exhausted do you see a drop in ORP?

yes

Frank, where did the cyano grow?

Ozone is the one thing I never experimented with in my reefs. Not sure why

on rocks the 180 was 75% bare bottom what ever sand I had in it got blown under rocks with the tunzes
when I was running Ozone the water was crystal,crystal clear ORP was around 490-500MV
I stopped using it I have bad lungs and although I used it in a reactor through a carbon reactor it still bothered me

 

[ellebelle]

even with PO4 down to .001 and my orp over 400MV I still had cynao
so.....

The thing about cyanobacteria is that it photosynthesizes and has nitrogen fixing capacities. So even if your phosphates are low, if you have ANY nitrogen in your system (which you do, even if it's not in the form of nitrates) and light (which obviously you have), cyanobacteria can grow.

 

[cali_reef]

6am Eastern... up late this morning?

It was actually few free minuets before dinner for me :shhh:.

I used ACIIIP to chart the ORP reading at two minuet intervals, it was very intresting to see the relationship to PH, salinity, temp, lighting cycles.. etc. ORP goes nuts when I feed the tanks too.

 

[meschaefer]

The thing about cyanobacteria is that it photosynthesizes and has nitrogen fixing capacities. So even if your phosphates are low, if you have ANY nitrogen in your system (which you do, even if it's not in the form of nitrates) and light (which obviously you have), cyanobacteria can grow.

Ellebelle is right, but there may be other things going on too.

Generally Cyanobacteria will require food to grow, primarly phosphate, nitrate and light. There are to many different strains of Cyano to think about and studies have shown that different strains need diffrent ratios of Nitrate and Phosphate. Some strains have a higher need for Nitrate and can grow even in a low phosphate enviroment.

The second problem is phophate and nitrate uptake. I think there is a tipping point wherein there is point at which there is enough of a nuisance (algae, cyano, etc.) to out compete GFO and Carbon reactors and an Ozone reactor for good measure. I.E. the nuisance, due to sufficient numbers, is able to utilize the nutrients before it can be run through a reactor or tested for.

The third problem, at least as I see it in terms of this thread is the concept that Ozone just masks an underlying conditon. I need to go back and look at the Ozone and ORP articles, but there was a point made when talking about ozone's effect on skimming. The Ozone breaks down organics making them less suceptible to skimming, but more readily available for bacteria. If this is the case, it is not unreasonable to think that use of Ozone (or any other oxidizer) could increase a Cyano outbreak (which is bacteria afterall). Seems counterintuitve (considering that some Cyano products are oxidizers) so I when I have a chance I will explore this further.

 

[ellebelle]

I agree on all counts, Matt. My only point was that depending on the strain that you have, it could grow in the absence of phosphates. Frustrating.

 

[meschaefer]

The fact that Frank had cyano outbreaks with a relatively high ORP, and the findings by Ken Feldman that his ORP readings where indpendent of his TOC (total organic compounds) level in his tank would seem to suggest that ORP is not particualry well suited to discerning overall water quality, but I think that there may be other things going on here.

In the article I referenced in the first post, Randy Holmes Farley states (and I paraphrase) that due to the complexity of Orp readings that any one particualr Orp reading is meaningless and not an indicator of overall water quality, and the findings of K. Feldman (second artilcle I referenced) would seem to support this.

In reviewing the graph found in the body of his article on organics, you can see that the Orp reading was not correlated to TOC. But, I wonder what you would see if that experiment was performed over a longer period of time.

In the data (the graph can be found here), you can see that over a weeks time that his Orp readings swung daily between 460 and 480, while his TOC readings swung between .7 and 1.35. With just this bit of information you have at best a base line as to how Orp and TOC change over a week's time. As we all know, Ph and temperature swing over a 24 hour period. Both of those components have an effect on Orp, and what we might be looking at is Orps reaction to other processes and not TOC.

It is possible that if water quality was allowed to decline (for this discussion an incerase in TOC) that the range in wich Orp swung might also decline. So instead of swinging routinely between 460 and 480, you might see a daily swings between 440 and 460 (I am admittidly making numbers up at this point). This relative decline might be a indicator that something is going wrong in the system (assuming that PH and Temp have stayed within their normal boundries)

 

[Bob 1000]

Very interesting, I've been following this thread.... But it seems like ozone breaks downs organic compounds too low if the skimmer can't readily export these organics... Wouldn't this be bad for someone that doesn't want to have to do water changes too much???
I will keep following this but for right now I don't see a good side except orp controller letting you know when your GFO which I don't use or carbon is ready for a change..
Hey guys keep posting more info, I'd like to know more from your experiences...

 

[Ken Feldman]

Randy sent me a link to this thread and asked me to comment. We did not examine ORP and TOC for a period of time longer than one week, so I cannot provide any further info about whether these two metrics might correlate over a longer time frame.

If you are trying to think about ORP as an indicator of water quality, you might want to first determine what ORP actually measures. I've never seen more than speculation on this point. In general, ORP electrodes probably (my speculation now) pick up the presence of compounds that readily gain/lose electrons; in the marine environment, it is likely (my guess, again) that the majority of those types of compounds contain quinone chemical functions, although some other chemical groups, and some types of metal ions might also be picked up by this measurement as well. So, if this speculation is appropriate, the issue then becomes, "how much of the DOC (dissolved organic material) contains quinone-bearing compounds under a given set of tank conditions?" That is a big unknown, as the chemical composition of DOC is not known. Nevertheless, it is possible that one set of tank conditions (food added, corals, especially soft corals, present) may produce one concentration of this specific chemical entity, whereas another tank condition (different food input, different coral populations) might produce another concentration. So, in the absence of further evidence, comparing one tank's ORP to another tank's ORP readings are not likely to lead to a meaningful conclusion. Likewise, a plan attempting to correlate OPR with some other water parameter, or even overall water quality, is likely to fall victim to the same problem; if the ORP reading changes, it is only telling you that the conc of electroactive species (i.e., quinones) is changing. If these electroactive compounds constitute only, say 1% of the overall DOC, then this changing value is not really telling you very much. So, the real question is (as noted above), what's in DOC?

That question is very hard to address from a scientific standpoint. In principle, the scientific instrumentation is available to begin to probe this issue; it is a high-end liquid chromatograph-mass spectrometer with ion trapping capabilities that costs ~ 1 M. People who have access to these instruments typically are exploring biochemistry research (i.e., How do the chemicals inside a cancer cell change when the cancer cell is treated with an anti-cancer drug?) and would not be inclined to "loan" out their instrument for aquarium research. However, we are trying to get one at Penn State, and one of the mass spec operators happens to be an aquarist. So..... with a little luck and a little patience, we may be able to finagle ourselves some instrument access to probe the DOC question (in a few years!).

Ken Feldman