Can these ORP readings be correct?

[kernnell]

Hi there,

I bought a new ORP controller, but I’m having doubts about the readings.

I have done several tests and the results are:

Glass of tap water – 450mV
Glass of tap water with a soup spoon of salt – 230mV
Sea water from a nearby pear (no very good water) – 200mV
Glass of mineral water – 250mV
My aquarium – 150mV

Do you guys think that these values are correct?
Is it normal that the tap water reading drops from 450mV to 200mV when I add salt?

Thanks in advance and best regard, from a fellow aquarist from Portugal.

(Hope you can understand my English)


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[JetCat USA]

if you're tap is not from a well then it's most likely got chlorine in it which is an oxidizer and it will have a high ORP reading. if you aerate it once the salt is added to bring the pH back up it should raise the ORP as well. if your tank is very neglected and hasn't had a water change in forever it could well be 150mv too.

[kernnell]

Hi there,

Thanks for your answer :),

The tap water is not from a well it comes from the city pipes.
I´m making new water I´m going to aerate it has much as possible, i´m using a 3000L/h (792 US gallons) skimmer pump (with air mix) on a 25L (6.6 US gallons) recipient. Tomorrow I will post de results here.

As for my tank, apparently I have no problems, al the fish are eating normally, I have no algae and all the corals ok and growing, i always make a 10% water change every week and clean my skimmer every 2 days.

That’s way I can’t understand these values.
:rolleyes:

[kernnell]

Any wane else? I would like to hear more opinions?

[kernnell]

help :confused:

[USC-fan]

what ORP kit are you using? I took weeks for my ORP monitor to read correct.

150mV seems really, really low.

[kernnell]

Hello again,

I also think so smoker… and I´m very afraid a use this to control an ozonizer and screw up everything.

It seems like I only get credible results with fresh water…

I´m using this kit: http://cgi.ebay.co.uk/PH-ORP-2-in-1-CONTROLLER-ELECTRODE-SOLUTION-CO2-220V_W0QQitemZ230171975422QQihZ013QQcategoryZ3212QQssPageNameZWDVWQQrdZ1QQcmdZViewItem

Except for the probes, that are like those but in black.

The experiment I mention above (25L recipient…), had a result of 140mV in 24h. Can this be normal?

[USC-fan]

i use a ozonier without a ORP monitor/controller. I just set my ozonier to a low setting. You really have to be putting A LOT of ozone in your tank to cause problems.

[kernnell]

Problem solved!

As i suspected, the controller wasn't giving correct values.

I was thinking about kb-smoker answer, and I realized that
maybe the probe had some kind of protective grass (or something) that was preventing it from delivering correct values.

I cleaned the electrode with a tooth brush and some soap and now my ORP is at 270mV
:D