Ways of estimating waste and bacterial growth in Moina cultures

Ways of estimating waste and bacterial growth in Moina cultures

As I said it’s just not about Ammonia. We need to figure out a way for estimation of Bacteria in the water and also we need to figure out a way to measure oxygen both of these measurements will assure us whether they die due to Ammonia or anything else.

1 Like

Actually you do - with some tinkering.


There are several such resources online that describe using a cell phone as a colorimeter.

Due to wide variation in image acquisition and post processing in cell phones, our results are likely to vary wildly between different camera models. There are however mitigation methods too. AFAIR I posted an article on the image problem in cell phones in the DIY microscope thread.
After we try out the above, we could use a standard camera that provides raw output coupled with a tungsten lamp to do an even better job.

Of particular interest is the multi disciplinary nature of the problem.



Additionally estimating the uptake and replenishment of NPK in aeroponics and hydroponics would be very good. The above method could be used to have a wholly automated system.


I am trying to wrap my mind around it but could you simplify a bit the principle and the process by which we use smartphones as colorimeter. I saw the apps but I didn’t understood this section of the reply.

I also didn’t got what you mean by NPK.

1 Like

Camera, lens, optical filters and image processing software vary widely between different phone models. Consequently an object photographed on one camera will look different on another.

The mitigation methods involve using a standard image-lightsources and generating a difference component, then using software to incorporate the difference so that one has the original image independent of the phone camera.
Using a regular camera that can give a raw image removes the need for such a complex calibration.

Here is a link about the method f calibration.
Colorimeter-cal-oe-27-14-19075.pdf (2.3 MB)

Nitrates, Phosphates, Potassium - nutrients in plant fertilizer.

Take a light source. Take a sample and add a suitable staining reagent. Shine the light source through the sample. Measure the light intensity passing through the sample using a sensor - your camera in this case. The camera has an app that takes the individual R,G,B values of the image and gives a quantitative measurement of light received and consequently the light absorbance characteristics of the sample. The rate of change of color provides quantitative information.
The first link page 32 onwards provides good explanation.

CAVEAT: My chemical and biology fun ended in school several decades ago.


Details for spectrometer

Several companies make light sensors - TI, Analog, Maxim, Vishay, Kingston etc . Datasheets of possible sensors for use in colorimeter and spectrometer.


A simpler approach :


Please give everyone a short summary on this video. @pratittodkar

1 Like

The Theory of the video

1 Like

Use this app

1 Like

Let’s try it out and identify advantages and disadvantages over a more conventional approach.

1 Like

I searched a little bit on the internet the only problem with this method is that the Beer’s Law fails for higher concentrations


Can everyone test this method on there own or is there a need for any further explanation?

what do you mean by Beers Lamberts law? What is it exactly?
How does it fail?
can it be coped up?

1 Like

It will be great if mobile can be made into a colorimeter @jtd @pratittodkar


@pratittodkar pls explain what is the purpose of this app?
How will it be useful?

1 Like

The only perpose of the app is to note the R G B values of the light coming after passing through the sample. And we can note down the values and then we can calculate absorbance using the intensities.


Beer-Lambart Law states that the absorbance is directly proportional to the length that the light travels through the container and the concentration of the absorbing compound in the medium.

Absorbance = epsilon (constant) * concentration * Length of the light that passes through the medium

Absorbance is an phenomena due to electrons ( hence a electric phenomena ). In higher concentration the charge density of the substance that is going to absorb is affected due to interaction with the solute and other potential molecules that might be present. Hence Beer’s Law fails for around >10mM

I haven’t found a source that makes it possible for us to cope with it.

We can either use that or the defination of absorbance which is
log [ I / I (with zero concentration) ]

1 Like

Ask for any explanation if needed and try the experiment as soon as possible.