Almost no "carpeting" plants will do well at low light levels. If you have less than 2-3 wpg you could try dwarf sag or dwarf hairgrass, but no guarantees on them. The other option is java moss.
If you are referring to the 29g tank in your sig, I'm not sure how well small foreground plants would do with goldfish, as I understand they tend to eat most plants. HTH~