Bark media and fertilizer

[notsogreenthumb]

I recently just repotted my Phalaenopsis in a mixed media containing Fine grade fir bark, charcoal and coarse perlite.

I read somewhere that because I'm using bark that I need to change from my 20-20-20 to a 30-10-10 because of something to do with the decomposition of the bark messing with nitrogen levels.

What truth is there to this and should I run out and get a different fertilizer? Also, with a different ratio, do I continue with my weekly half strength fertilizing?

Thanks,
Dustin