How much RNA is needed to see rRNA on a gel? - (Jul/29/2009 )

I have RNA extracted from E. coli with GFP in it using trizol. I spec.ed it and i got 50 ng/ul. Is this enough to see rRNA on a gel? what is the least that i could go until i saw no product?

nm, i found out that you need at least 200ng/ul. so i have 250x the total concentration needed.
(I have RNA @ 50ug/ul. only need .2ug/ul so 50/.2=250)

Normally a 10ng DNA band is easy to see on a EtBr staining agarose gel for me. RNA I feel like if I have more than 20ng loaded on gel, I can see clearly at least one band (drosophila) around 1500bp (a DNA ladder), and a faint band at ~400bp. I am not sure whether I'm right, I thought the 1500bp is rRNA.

thanks man!