An aquarium

It seems that the only things doing anything in my aquarium are the fish. They swim and feed. They breathe using their gills. There must be more going on!
There's some pond weed there and some green algae. If they are living, and they are, they must be doing something - why would the pet shop say that the plants were good for the fish, even if it doesn't eat them.


diagram

In fact, the plants are producing oxygen but apart from some bubbles, that is hard to see. Another way to 'see' oxygen is to use an oxygen sensor. This can measure the amount of oxygen in the water so when the oxygen level increases you can see this on a computer screen.
You'll know that plants need light to live so you would expect that the plants will be affected by day and night. So I've used a light sensor in this experiment on my aquarium where I'm trying to see what the plants are doing.

What I did

I placed an oxygen sensor in an aquarium and set up a light sensor nearby. I connected these to my computer*, started it running and left it disturbed for several days.

*Actually rather than leave the computer running all the time, I used a data logger. This is a box which will automatically take readings from sensors over long periods of time.

Gratuitous special effect - you miss little  

The results

results of light sensor  
This is the graph of my light sensor.
  results of oxygen sensor  
This is the graph of my oxygen sensor. It looks bumpy or 'noisy'.
  results of both sensors  
This is the graph of both sensors on the same axes.

You will find some of the following questions easier if you put these results into your data logging software. Click here to get the results, then Open it in your data logging program.

Look at the first graph of the light level:

Extra:

 

Look at the third graph showing both oxygen and light level:

What you might find out


Idea and results file by Laurence Rogers, University of Leicester.