I see a ton of blackwater biotopes that don't use plants at all, mainly driftwood and leaf litter. Here is an example:
http://showcase.aquatic-gardeners.org/2011/show38.html
I'm sure if you're set on plants something like Java moss would be the way to go though.
http://showcase.aquatic-gardeners.org/2011/show38.html
I'm sure if you're set on plants something like Java moss would be the way to go though.