Stubby,
From a study design standpoint, there are some improvements I might recommend. Assumming you only have 4 tanks, I would place the same (exact) amount of sludge/leaves/food in each tank (carefully weighed/measured). Have one tank with no aeration and no bacteria (the control tank, which is what your original design was lacking), one tank with with just aeration, one tank with just bacteria, and one tank with aeration and bacteria. Ideally you would have replicates so that means and variances could be calculated, but it's probably not practical and you probably won't be publishing the results in a scientific journal:) Use the same amount of bacteria in the two tanks that get the bacteria. Use the same amount of aeration in the two tanks that get the aeration.
Just be sure to use the exact same amount of organic material and water in each tank. Come up with a standardized way of measuring the organics so that you can later test for reduction. This can be done by weighing the material and measuring the "depth" of the material once it is laid out flat and even at the bottom of each tank. I would plan on doing the measurements every month so that you can track the decay rate...if it does exist.
Also be sure to write down everything you do including the amount of water, bacteria used, monthly measurements, etc.
I'm very interested in your findings and I hope you keep us posted as the experiment persists. Take some photos, too!
Good luck. Shawn
