Kelp maybe?

[Mave26]

Hey guys,
I'm wondering if anyone could tell me what in the world this is. It seems to some type of dark red plant. I thought maybe kelp but my Cole Tang isn't touching it, neither is the mythrax carb. And those two little guy eat just about anything.

[karlas]

it sort of resembles a sea lettuce of some sort but sea lettuce is usually green im not sure if there is a red variety

sea lettuce (http://www.vattenkikaren.gu.se/fakta/arter/algae/chloroph/ulvalact/ulvalae.html)