Testing ORP

[Russ W]

Hi Andy,

Do you have a calibration buffer?

As with any electronic test equipment, you should have a standard to test against.

Although you can buy such a solution, I had the lab where I work make me a solution. The mathmatical calculation of what this solution should read was 460 mv. When I placed my meter in it I got 458.

I guess thats close enough for me.

Russ

[GazKoi]

Yes I agree with you Russ if you use this type of equipment you need to calibrate it and keep an eye on it


I regularly test my meters with the calibration solutions to make sure they are OK.

Andy if the battery warning is on try changing for a new battery and see what it reads then.

[RobR]

A couple of more points about ORP readings is that they will also change with the seasons.

In the summer when you are feeding heavily and with the warmer temps of the water your DO levels will be lower....hence a lower orp reading.

Just the opposite in the winter. Cooler water, higher DO, less feed will result in higher orp numbers.

Ph also plays a big part. The higher the ph, the lower the orp.

I try and use mine to see trends in the water quality and clean it regularly. Once a week I scrub the probe with a toothbrush and about once a month I soak it in ORP cleaner. If you don't keep up on probe maintenance you will get readings higher than actual water values.

[Rich L]

Once you have a calibrated meter, you can set up a 'check your calibretion' event at the club'e next meeting and use yours as a standard. Same with pH , etc meters.


A thermometer can be checked using a water/ice slush. When they are both well mixed, they both will be at freezing. I write the error on the back of the particular meter and use it when I need accurste readings. Most of our readings can be a couple of degrees off without impacting our goal. The differences will remain relative.

Remember to check both probes on differencial measurements. If you have an inside/outside meter, the inside portion can be checked by allowing both the calibrated (outside) probe and the inside portion settle out and check the error found by compsting thr two and accounting for the error discovered in the outside probe earlier. The outside probe should be laid on the port on the meter so they're in similar environments. Compare the two and recheck in a minute or two. Once they have settled you can compare them.

[Nishi8]

...........................

[Bancherd]

I used to make ORP measurements everyday and became very depressed with the numbers .

The probe is now broken and I no longer make ORP measurements.......I am VERY happy .

[dick benbow]

can appreciate what your saying! LOL!


It's like the olde saying about beating your head against the wall, once you stop it's a big relief!

[Grove]

Gents

Where abouts can you get Test solutions for orp calibration in the UK. Have tried and failed up up till now and hope you can point me in the right direction.

Have three ORP probes and two meters but have nothing to recalibrate against

Cheers

Grove

[Rich L]

Hi Andy,

Calibration checks for maters and even our standard water test kits is valuable.

The themperature instruments can be calibrated with water/ice at the same temperature. Ice can remane frozen at 32 degrees and water can remain unfrozen at 32 degrees. There's a transition that requires heat to move either way to cause the change.

If you take crushed ice and mix in enough water to form a thick slush, both the ice and water will be at 32 degrees and you can use that to calibrate your instrument. I do that with new instruments and if there's no way to calibrate them I just mark the difference with a peice of tape on the back.

If you have three meters, you can use the two closest together as a reasonable guide for our purposes.

You're right about mercury thermomiters unless there's a bubble in the mercury.

[Aussie Koi]

This is one of the best pieces written on ORP. I stole this from NI and was by JR....

The recipe for a high ORP values

The way to get a high ORP reading is not to live and die by what a meter tells you. That is a good method to detect pollution building but can also be misleading. Lets cut to the chase- the use of an ORP meter by someone who does not have a greater understanding of how a good pond should ‘look’ is a waste of time. Instead become a keen observer and critic of your own pond. You want to come to be able to see things as they develop. So here are some areas that are absolutely inconsistent with low ORP readings and some others that are consistent with very high ORP readings, If you have these things don’t worry about the meter.

A pond that has water with a certain ‘look’. What is that look? Water that has a shine at the surface and the water looks very fluid- never thick, yellow or murky. It’s not as much about super clarity as it is about a look of highly biologically conditioned water within a closed system. This does not mean ‘exhausted’ or ‘spend’.

The aeration and waterfall create bubbles that pop within seconds of forming. There is no foam or rafts of bubbles anywhere on the pond surface. No escaping bubbles last longer than five seconds- count it!

The floor of the pond is clean and no bits of waste can be seen

The filters may contain some mulm but it is odorless and light as a feather- easily moved with a simple movement of two fingers waved above it. You should notice that in between flushing, the mulm tends to disappear.

You exam the water or detritus on your filter media under a microscope and see some forms of
life- typically protozoa and crustacean forms.

There is never any sign of white fungal growth within the vortex and the vortex never has an odor other than the smell of ‘top soil in the garden’.

You have not experienced any sign of bacterial infections yet you haven’t used a pond additive in many years.

Between water changes, your pH sits between 7.0- 7.6

You haven’t seen any nitrite in your pond system since the days of new pond syndrome.

Your pond algae is only on the walls of the pond and is a very bright green. The length is short ( 1/8-1/4 inch) and the koi spend hours a day browsing along that material. There is no red, brown or string algae dominating the species mix. The higher the ORP the less the micro algae growth in general.

You never ever see koi sitting at a 45 degree angle to the surface or the pond floor

You see regular steady growth from all koi in your care

Koi under three years old grow in the winter albeit at a slower pace ( with little or no food )

The koi show a very high quality luster

The koi’s slime coats are present to the touch but never truly dripping. And the koi never feel like sandpaper to the touch.

Koi colors remain vivid and you never see a blotchy appearance to the reds. White ground is uniform and no yellowing is seen in the face of more than one or two individuals. No red veins are seen in the white- including tancho which are your ‘indicator’ fish in any pond.

Koi show increased activity or leave an impression of being ‘happy’ always and not only immediately after a water change.

The koi always have an aggressive response to food added to the water


The environment just described can be obtained without additive products if you design and approach things correctly. This should be every hobbyists experience after a few years in the hobby. Unfortunately it isn’t often the case. But IF you have these things and you are wondering about your ORP reading I assure you it is high! Typically in the 250 -325 Mv range. ORP in ponds is HIGHLY dependent on stable pH and saturated oxygen levels. The addition of a TT as a gas exchange unit is likely to buy you an addition 50-75 Mv. Hope this helps expand the notion of ORP. JR

MCA

Good, pond walls
quite area of ponds
the biofilter - but not the nexus or TTs

Bad, under air bubbles from aeration
the primary vortex
the skimmer box

Do not fix on the number , fix on the range

Ponds will typically show a range-

**example: ( use as guideline only)
Terrible - 140 Mv - 180 Mv
bad pond - 180 Mv - 220 Mv
fair pond- 220 Mv - 260 Mv
good pond- 260 Mv - 320 Mv
Excellent- 320 Mv - 380 Mv
Super pond 380 Mv - 440 Mv

pH 7.5
temp 78 F
oxygen -saturation


JR