Most of this I have under control as I'm a bio major with an emphasis on natural resources and soils. I understand the nitrogen cycle, BOD, CEC (which stands for cation exchange capacity - you were close), macros and micros...
What I particularly need help with is specific conditions for specific aquatic species. I'm into soils and have a bit of experience with hydroponics so I know what conditions (EC, ppm...) that terrestrial plants require but I have a feeling that 1600ppm of nitrogen, which is fine for tomatoes, isn't going to be great for fish...
My 10 gallons will need to be redone and I would rather go with organic slow release soil than have to dose with nutes. At the moment though my focus is on this 20 gallon.
I see that people here have decent results with Miracle Grow organic which I have used before (non aquatic) and find runs very hot (high high quick release nitrogen levels). I'm using an organic potting soil base amended with half mineralized high nitrogen bone meal, alfalfa meal, and a tad of kelp meal - it should be very similar to Miracle grow but with a slower nitrogen release pattern and a lot less urea and salts.
I have capped my soil in river sand and set up some simple hard scape and am now awaiting my water to sit so I can start stocking it with plants. I know a bit about plants but very little about specific aquatic plants but this is what I am thinking -
fissidens fontanus - next to base of tree
glossostigma elatinoides - sides of river
Hemianthus callitrichoides - tiny tiny ground cover for whole tank
Hydrocotyle verticillata - towards the back?
Riccia fluitans - even better ground cover for the tank.
Crystmas moss - for rock/base of trees
Vallisneria nana - long grassy plant for back of tank - two on each side.
Java moss or something similar for the tops of the trees.
This is the filter that came free with the tank - Might modify it just a bit. I also have several sumps if I choose to go that way later.
Light will be one of my DIY CFL rigs that I use for indoor lighting. Some people don't seem to realize it but CFLs are the exact same (actually better when it comes to penetration) as T5HO bulbs. I can run anywhere from 1-12 bulbs with my rigs but I'm thinking I'll likely go with 4 23w 6500k unless I can find some cheap 10k bulbs to mix the spectrum with. If this is too much or not enough light please let me know - 92w over a 20gallon.
A DIY C02 is in the works as well.