I first got this idea of the coffee fertilizer from Dave Evans from a thread he had posted on the Carnivorous Plants in the Tropics website. I decided to try it out for myself and actually gave all of my Neps one coffee treatment. My results were posted on the OCPS website on this thread:
From Feb 5, 2009
From May 2, 2009
Recently from Aug 3, 2009
I took pics, from left to right, of N. macrophylla, N. villosa and N. rajah. They were fed coffee in January of 2009. I took pics of them on Feb 5, May 2, and finally on Aug 3. 2009. The rajah was removed from the tank because it was getting too big, so I just substituted another villosa in it's place. The results of six months of growth can be seen for the macrophylla and villosa though. Not sure if it proves a whole lot because I didn't have any controls in place, but it certainly didn't seem to hurt the growth rates or overall health of the plants, with just one coffee treatment being applied. I should try and get in touch with Dave Evans and see how often he would recommend these tonics can safely be applied. He might have some newer ideas to do with this coffee fertilizing.