Once a low tech tank is matured it can be relatively self sustaining depending on the plant spieces in there of course.. Easy plants will not nessecary say it aint a heavy feeder. I got a little 25 liter low tech running on akadama, not sure but i think it's about 8 months old now.. It rarely gets ferts and i use it as plant bin, so all the trimmings i do not want to dispose off end up in theis little tank. So it's pretty heavy planted. Even tho i do not fertilize it and it's very low light plants in there hold on pretty good and grow. Mainly there are java ferns in there some bolbitis, bacopa, Lilaepsis Brasiliensis, potamogeton gaiy, some others, a few floaters and a load of mosses. All grow relatively good the only one in trouble is the blyxa, but still alive.. It kinda runs on it's own debris providing ferts.. Even have to water change regularly because of the cyano developng on the surface. So it even provides an excess of organics. 🙂
So yes any plant needs ferts the same as we need to eat.. But a tank can provide it's own needs.