Lets talk ORP

[nicco]

Is there any other way to measure DOCs levels?

Well perhaps you should go back and read the first few explanatory posts again. ORP meters do not measure DOCs directly either. Don't think anyone brought those up. Any decay or reduction process in the pond including the decay of solid materials affects ORP - say dead skin cells from fish.

DOC's are a separate topic and perhaps deserves a separate thread. How would you measure DOC’s? First you’d have to know what they are as they can be many things, then some combination of meters may help out – say TDS (since this measures total dissolved solids and is typically calibrated to one ion), ORP (because decay of DOC's will be a component of the total decay in the pond) and turbidity (for DOC's that stain the water) meters. Better to avoid the problem altogether by having a filtration system matched to your stocking level and doing regular water changes.

[Noahsnana]

Well perhaps you should go back and read the first few explanatory posts again. ORP meters do not measure DOCs directly either. Don't think anyone brought those up. Any decay or reduction process in the pond including the decay of solid materials affects ORP - say dead skin cells from fish.

DOC's are a separate topic and perhaps deserves a separate thread. How would you measure DOC’s? First you’d have to know what they are as they can be many things, then some combination of meters may help out – say TDS (since this measures total dissolved solids and is typically calibrated to one ion), ORP (because decay of DOC's will be a component of the total decay in the pond) and turbidity (for DOC's that stain the water) meters. Better to avoid the problem altogether by having a filtration system matched to your stocking level and doing regular water changes.

Again thank you nicco... I am learning

Yes I believe it is time to start another thread concerning my last question.

[Roddy Conrad]

A TDS (Total Dissolved Solids) meter is just a conductivity meter with a calibration to read conductivity as total dissolved solids. Conductivity meters are also sold with a slightly different calibration to read out as % salt in the water. The conductivity is "mainly" affected by dissolved salts, and only slightly affected by the DOC level, in most pond waters. There are exceptions for sure to any generalization about ponds!

ORP does more directly measure DOC content. But the ORP reading is affected by many variables, to name a few:

1. DOC content, higher ORP readings mean less DOC content, if the ORP reading is below 150, the DOC content is really too high to be healthy for the fish.
2. pH value, higher pH gives lower ORP readings, lower pH gives higher ORP readings. For example, dropping the pH from 8.3 to 6 without anything else changing but pH increases the ORP reading by about 100.
3. Temperature, lower temperature gives higher ORP readings, increasing temperature from 50F to 85F drops ORP reading by 50 to 75.
4. Lack of routine cleaning of the ORP electrode gives a slow drift upwards to the reading from the meter, if the probe has not been chemically cleaned for over a week, the usual behavior is the meter is giving a false high reading by about 100 points.

[stephen]

Excellent post Roddy

[Noahsnana]

When reading what MCA posted re: roddys link at KoiVillage on ORP I read it as ORP registers pollutants.... and I related it to DOC's

[nicco]

Be aware that you can get low ORP and low DOC's too. So it's not the perfect indicator.

Some Brits have been using TDS meters to measure DOC's, but it's a little iffy. It's a bit like depending entirely on your ORP meter. What they do is they measure TDS of fresh water that they put in the pond after whatever treatment they employ. Then they keep track of the TDS readings in the pond. They set a threshold where, if an uppe value is reached they deem it time to refresh the water, or the continuously feed new water into the pond to maintain what they think is a reasonable reading.

The thought behind this rightly or wrongly is that any additional dissolved solids that turn up in the ponds is due to waste. It works for them.

The fact is that many top end koi keepers don't use either ORP nor TDS. So take it for what it's worth.

Stephen on the other hand has a couple of dozen of them and from his recent posts on his pond he doesn't trust any of them. Hey Stephen how about an update on that thread?