All the talk about duckweed has prompted me to write about my 
observations with growing the stuff. Once i started growing plants I was 
told "never ever get the stuff, or you will never get rid of the stuff". 
Recent postings on duckweed concur with that observation, however I have 
never been able to grow it. It is not a water chemistry problem, I grow a 
reasonably large number of plants to a presentable standard. Australian 
and Papua new guinean rainbowfish eat it. Several times now i have had 
plants come in with it from the store and it never lasts more than a 
couple of days. The trifasciata's that I have seem to particularly enjoy 
it. This is just a suggestion to anybody that is trying to get rid of it 
from their tanks and are sick of trying to remove it themselves. A few 
adult rainbows get through a lot of food and are always looking for more 
that they can eat.

Have a  good day

Peter Hughes