Continuous monitoring vs intermittent testing

For the sake of conversation I would like to present some visuals.

I get a form of this question a lot: What’s the difference between continuous monitoring vs intermittent testing. What they’re usually asking is something like “What’s the difference between my api test kit weekly and a submerged pH probe”

I would suggest that they probably couldn’t be more different.

Here is a farm that ran an experiment. They wanted to see what insights they could see between an api test kit and the probe.

You can see when put next to each other the test kit really just shows you if anything is wrong/right at that particular time. The submerged probe gives you a full sense of what is going on over time and you can identify trends.

Then it gets even more interesting when you compare it to your other notebooks like fish deaths, light intensity, harvest records, or even lab tests, etc. Here is a fish death with pH change example…

Do you have any other examples where this is helpful? What other ways could we push towards continuous monitoring so we can understand more and geek out?

2 Likes

While the graphs at first glance seem to support this statement, looking at the y-scale reveals that the intermittent test swung between 7.4 and 7.6 with a mean of 7.5. This is fine and expected. The continous monitoring is of course more detailed, but in the end it has a mean of roundabout 7.5.

If you were to testing the pH daily or every other day, and calculated a sliding average of the past three measurements I’d suggest that you’d have a value you can safely operate a system with.

pH swings of 0.1 up or down usually should not pose any risk to the fishes.

In the second graph I can not see why you suggest that it exposes more information. Are you suggesting the fish died because of the low pH on th 15th?
Taken as a sole source of causation I’d deem that unlikely.

Yet I am not advocating against continously monitoring water parameters. On the contrary, I’m strongly advocating pro. We just have to take care of the probes and remember that there can be a significant drift over time.

Some measurement systems simply give you the raw voltage measurement data which you’ll have to convert into the pH value.
How are you handlying calibrating the probes in such a system?
Seriously interested what you’d propose as a best practice.

The fundamental difference between continuous and intermittent is the same as comparing a snapshot to a video. In research studies, we try to minimize variability with the snapshot approach by collecting water samples at the same time each day and before feeding. The challenge with continuous monitoring has been reliance of the probes. Automated monitoring is desperately needed in several aquaponic applications!

1 Like