I have a 1.5-2 gallon hex (not 100% sure about tank volume) that I've setup with some cherry shrimp in it. I have a 23 watt CFL bulb in a fixture on top of the tank that lies horizontally. I put 1mL of liquid carbon in it daily and root tabs once a month. I realize that doesn't necessarily qualify as low tech, but because its so small it requires very little in terms of liquid carbon and root tabs. Also maintenance is very low. I have to be honest, I really think my tank would be perfectly fine without the daily carbon and monthly root tabs.
Dwarf hairgrass carpet
Ludwigia repens (background)
a tall and thick grass of some sort (can't remember the name)
anubias nana narrow leaf tied to cholla wood
The java moss grows the fastest, but the ludwigia is pretty fast growing too. If I wanted a lowlight setup I'd maybe use a 16 watt CFL instead, but honestly with the little cost of the liquid carbon you might as well just put the plants in it that you want. You can really only put invertebrates in a tank this small anyways so algae is no problem (it wasn't a problem before I stocked the tank either).
I really think you could do this without carbon or fertilizers. I use them for the added benefit, but things would likely just be slower without them. The important thing to keep in mind is that maintenance with a small tank can be a huge pain (trimming plants etc), so be sure to choose plants that aren't gonna have to be trimmed all the time to maintain the look that you want. Good luck!
Last edited by GrantF; 03-02-2015 at 04:04 AM.
Reason: added info