I have many Anubias varieties, including the nana
, and they definitely do not need ferts or special lighting to thrive. I attached mine to a tiny piece of driftwood and decor with a rubber band and by the time the rubberband split and fell off, the each of the plants were attached. I literally do nothing for these plants, and they are propagating beautifully.
I have the Anubias nana in my 2.5, and it works really well in that size tank. The marimo ball is also a good fit.
Edit: Though all of my tanks do have a filter, I don't think not having one would have an impact on either plant. The plant'll feed off the nitrates.