more water changes equal lower orp?

[roons]

up until 2 weeks ago i had been doing 25 gal water changes once a month on my 120 gal tank, my orp had been 330-360.......i started to try 10 gals weekly last week, after changing 10 gals my orp dropped to 295, stayed there for a day and by yest ( a week later) it was up to 330....................today i did another 10 gals, its now at 278 and i fear it will only get up to 315 by next week .........................why is this? i would think more water changes would bring the orp up , not steadily decrease it.....:confused: using 0 tds ro/di also


25 per month = 330-360

10 gal first week=295-330

10 gals this week=278-?

[E-A-G-L-E-S]

what is orp

[Randy Holmes-Farley]

Saying that more water changes would bring up ORP makes the faulty assumption that ORP is directly related to water "cleanliness". It is not. It is a very complex combination of many factors that results in a particular ORP value, and fresh salt mixes often have low ORP. If they have, or you use a dechlorinator, they will have especially low ORP. Have you measured the ORP in yours? It also changes with the time during the lighting cycle, so you need to measure the same time every day to track changes correctly.

In short, however, I would not suggest equating ORP with water quality.


what is orp

This article should explain all you need to know about the redox potential of the water (ORP):

ORP and the Reef Aquarium
http://reefkeeping.com/issues/2003-12/rhf/feature/index.htm

[roons]

i use crystal seas bioassay formula , it has no dechlorinator, i have not tested it by itself no, but i thought for sure by me removing 10 gals of used water the orp should go up, i guess i was wrong..............im sure by doing more water changes im making the tank cleaner, do you think orp will continue to drop or will it level off? and those levels were the low right after the water change and the high a week later, yes i know values are different at different times of the day , lights , ph etc......

i guess this just has me confused, is one big change with higher orp better than 4 little changes and lower orp?

[Randy Holmes-Farley]

I wouldn't expect that the ORP will continue to decline significantly in the tank unless your husbandry practices change.

I do agree that water changes are beneficial. :)

IMO, ORP is a near meaningless number for a reef aquarium in the context of water changes, so I would not try to decide how to do them based on ORP changes when it takes place.

[roons]

ok, ive read your article before, unless im wrong i thought orp is a rating in mv of the waters ability to break down organics, i assume a lower value would mean the water cant break them down as easily than a higher value.........your actually removing organics when you do a water change, i would think the overall volume would contain less organics and the ozone wouldnt have to work as hard to break them down, i guess this is why i dont understand it going down..................allright , ill see how it goes in the next few weeks, i have a feeling however its going to continue to go down............

[Boomer]

rooms

As Randy has metnioned it is a very complicated issue and is not understood much. Second, just for the sake of argument, the ORP of a fresh IO mix is only around 275 mV and has no organics. Yet many well run reef tanks, with no ozne, run in the high 300's mV

your actually removing organics when you do a water change, i would think the overall volume would contain less organics and the ozone wouldnt have to work as hard to break them down


That is true, meaning the ORP will rise quicker and less ozone will be needed to raise the ORP to X level. It is a very complex combination of many factors and that new water does not have that YET, a complex combination of many factors going on YET

[roons]

Originally posted by Boomer
rooms

Yet many well run reef tanks, with no ozne, run in the high 300's mV


how can this be?



It is a very complex combination of many factors and that new water does not have that YET, a complex combination of many factors going on YET [/B]

so this being said, am i better off with orp 330-360 and one big change a month, or orp 275-300 and 4 small changes a month, at this point the number on my monitor doesnt tell me much........

[Boomer]

how can this be?

Very efficient skimming, scheduled water changes, high capacity pumps, good circulation. removing detritus, watching water parameters that can be tested for, not to exceed the bioload, etc..


I would start a water changing schedule and stick to it, say 25 % net volume/month. The ORP will come up in time. Just because "Bob's" tank has an ORP of 390 mV does not mean it is healthier than your tank with 350 mV.

and 25 per month = 330-360

+ how can this be?..... run in the high 300's mV...

Are you using ozone, if not those are nice readings. So, you are almost there :D

[roons]

i had allready started one, was doing 25 gals a month , my net is 110 gal................i thought i would be doing the tank better by doing 10 gals a week instead( 40 gal a month), now im not sure which im better off with.....................and yes im using ozone, or are you being sarcastic?

[Boomer]

and yes im using ozone, or are you being sarcastic?

No, not at all I used if for decades. Your post does not say if you are or not. Leaving me with the thought, you might not be and are getting 360 and you just can't get in the high 300's with out ozone and you can .

[Randy Holmes-Farley]

IMO, I prefer more smaller water changes, but that has nothing to do with ORP, but rather other stressors on organisms (like salinity, temperature, ammonia, etc).

[roons]

Originally posted by Boomer
and yes im using ozone, or are you being sarcastic?

No, not at all I used if for decades. Your post does not say if you are or not. Leaving me with the thought, you might not be and are getting 360 and you just can't get in the high 300's with out ozone and you can .


im sorry i guess i could have been checking orp and still not using ozone, my mistake i should have stated such.................as for getting high 300's without ozone it baffles me how this is possible when the more clean saltwater i put in the farther the orp drops................maybe they arent doing water changes at all............and then a fresh io salt mix has an orp of 275?

this all has me confused even more , maybe i need a degree to understand i dont know, if you were to start out with a fresh mix of 275 , the more organics that built up in it the higher the orp would go? or is the breakdown of the elements present in the water that does such.............geeze, i think im going to go back to one change a month, and put black tape over the orp readout ,lol

[sjvl51]

roons, this article explains the effects of large water changes vs small water changes - http://www.advancedaquarist.com/issues/april2004/short.htm

"After considering the result of changing varying percentages of water volume, I highly suggest 20 or 30% water changes, performed on a semi-regular basis. Usually every 2 to 3 weeks or whenever conditions in the tank appear to change or the water turns somewhat yellow due to the organic acids from decomposition building up."

Vickie

[grim]

Don't chase ORP numbers, you'll drive yourself crazy. Do not try to compare ORP numbers with others, don't look for target numbers or try to get your tank into some arbitrary target range, it's useless. ORP is in incomparable number.

There are only three "values" you need to be concerned with when monitoring ORP.

Below Normal
Normal
Above Normal

For your tank, it looks like 300-360 is "Normal". Like already said, fresh salt water has very low ORP, mine mixes to a low ORP, and when added to my tank, pushes the ORP to "Below Normal". I use ozone so I can push my ORP back to "Normal", in a few hours time. Now, if your tank falls into "Below Normal" and you didn't do a water change (or something else like dump a ton of food into the water), something is up, take a good look at the tank and do some tests. If your tank goes into "Above Normal" for a while, it could be time to shift your numbers upward (good strong skimming, siphoning, nutrient control, light feeding, all push the numbers up in my experience).

There is only one ORP "number" people need to know when using ozone, and thats 450mV, don't try to push higher. This goes against the "orp numbers are useless, it's the trends that are important" idea, and that's only because of tank safety reasons.

jb

[Randy Holmes-Farley]

roons, this article explains the effects of large water changes vs small water changes -

Actually, I totally disagree with the conclusions in that article. The author has confused the size of indivdual changes with the total amount of water changed.

Sure, X 20% changes changes a lot more than X 10% changes. The real question is whether X volume of water changes is much different at 5, 10, or 20% each. In short, te difference is very small, as I've posted many times.

[roons]

well heres even more of a twist, at the same time i started doing the weekly changes i threw a bag of carbon in the sump, i removed yest just to see what would happen, damned if my orp didnt shoot up 25 mv overnight from what it had been..........is it possible that the carbon was sucking up residual ozone and not letting it get to more of the organics in the water?

[Randy Holmes-Farley]

Yes. Are you not passing the effluent over carbon? I would not send ozone into a tank without passing the effluent over carbon before it got to organisms.

Remember that organisms are also organic, and ozone degrading organics means that it is also degrading the organism surfaces if it gets to them.

[roons]

no im not , im not sure i follow your second part.........as long as my numbers arent above say 400 wouldnt any residual ozone attack organics in my sump and the water column ? before it would go after fish? i havent seen any ill effects so far , 6-8 months now............but i do know my orp is higher without carbon in my sump................it was 295 this time yest, had been for most of the week , its 317 today............only change was removing carbon

[Randy Holmes-Farley]

no im not , im not sure i follow your second part.........as long as my numbers arent above say 400 wouldnt any residual ozone attack organics in my sump and the water column ? before it would go after fish?

Why? Ozone doesn't care if the organic molecule is part of a living organism or not.

i havent seen any ill effects so far

Perhaps it is fine. But things can also be far from optimal, and not be noticeable without side by side comparisons.