redox has always been one of those stats that is easy to measure but hard to understand.  there are plenty of sites and books that get into the nitty-gritty details about reduction-oxidation reactions.  but one of the best definitions that spoke to me recently is one that tries to abstract away the details.

redox is … a measure of the ability of a system to eliminate wastes

John Tullock – The Reef Tank Owner’s Manual

that statement made me think about my currently cycling tank.  i had recently calibrated my redox probe on my profilux controller, and it had an initial value of around 180mV.  since optimal redox values fall within a range of 350-450mV (Delbeek/Sprung), it was obvious that my redox was “low”.  then i began to think about what “low” really meant.  thinking in terms of the above definition, it means that my aquarium is less able to eliminate wastes.  this makes perfect sense when thinking about the nitrogen cycle.

since the proper bacteria for nitrification have yet to colonize my rocks and sandbed, my tank is doing a poor job of removing ammonia (the waste) from the water.  as my cycle continues and my bacteria population rises, my tank will better eliminate wastes and my redox reading will increase.  so theoretically I should be able to watch my cycle via my redox readings as they go from 180mV to around 300-350mV.

it all clicked for me when i was glancing at my redox readings today.  i noticed that each day the maximum measured ORP increased from the day before.  obviously testing for ammonia and nitrite is the true and correct way to know when your cycle is complete, but this sure is easier. :]

Tracking my cycle - Updated 12/14

Redox - 1 month later. You can clearly see when the cycle completed around Jan 2