My post, greenhouse-sensor-reading, noted an experiment to use the Sensor Egg to detect elevated levels of Nitrite/Nitrate in my aquaponics tank which are deadly to fish. I am happy and sad to note that the experiment shows that this thesis seems valid.
The theory here is that elevated levels of these chemicals in the water may trigger the N02 sensor in the egg and show a reading which can be used as an alarm.
What I found in two occasions was that an imbalance caused by overfeeding caused fowling of the water and triggered elevated readings in the Egg. If you look at 1-15-2013 and 1-27-2013, https://cosm.com/feeds/96569, you will see elevations. The second elevation occurred while I was travelling on business, and due to the length of time before I checked on the tank, it resulted in fishkill which caused a loss of about 50lbs of fish.
While I am not sure of the accuracy of the NO2 calibration of the sensor unit, it is sufficient to use the relative value as a trigger. I have the cosm feed set to tweet me should the value rise above 250PPB.
If you are setting up a new tank, then the Nitrates/Nitrites will be elevated while you are "starting" the tank. Use this to set your high point on the sensor readings. When your tank settles -- that should give the normal "safe" reading level.
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