Watercress? Though I've never heard of anybody growing it in a tropical
aquarium, it does get used in ponds.


I bought some straight from a grocery store and was able to grow it really
well in a low light environment. A word to the wise though- it came complete
with parasites, even from the grocery. I should have been more paranoid. It
does work though.

As long as we're on the subject, I believe duckweed is a perfectly edible
aquarium plant/pest.