Re: Non-Co2 methode. help me understain this..
Bacteria use O2 to break down organic matter(leaves, rotting/dying plants, dirt, soil, manune,Urea/Fish waste=> NH4=> NO2=> NO3 etc).
The more of any of these you add, the more the bacteria will remove the O2.
They will keep doing this as long as there is ample O2.
Once all the O2 is gone, then they start using anaerobic and fermenative pathways and many species of NO3 reducing, then Fe and Mn reducing bacteria appear and if there is a lot of waste and no O2 input, H2S and CH4 production may occur.
In the substrate, the flow in/out is limited, much more than in the water column, as the O2 is removed by bacteria, the Redox potential is lowered, going from 500-400mv in the water column, down to about 200-300mv for most Fe and NO3 reducing bacteria, Sulfate reducers will be down around 100 to -100 mv, and -200 and lower generally are CH4 producers.
Now in order for these higher levels of redox levels to be maintained, you need to have a steady rate of O2 supplied.
No issue in the water column, plenty of O2 generally.
In the substrate, the flow rate in/out is limited, so the lower redox values are produced.
Too low is not good(H2S production, very low O2, often rotting smells and por plant growth) too little is not good either(no reduction of Fe/Mn and in some cases NO3, plus good bacteria community).
Some folks add too much organic matter and /or do not place a large enough cap on top of a base soil layer for exmaple. Too much of the soil leaks out, drains the water column of O2, NH4 is often produced as the NH4=? NO2/NO3 producers don't have enough O2 to use since there's so much organic mattter that the bacteria go after that leaving little for the downstream decomposers of NH4 waste.
Then you get algae.
If you presoak the soil 2-3 weeks first in shallow tray, then organic matter has been mineralized already and you do not have such issues.
But folks can add the right amount of soil and do fine also, it's just more folks will have better success rates since many make mistakes initially if they soak the soil first, or you may boil it 15 minutes instead(Sterilized the soil though, no bacteria are left) but it does stink up the house!
Regards,
Tom Barr