I have used philodendrum stems, I know them as pothos, in betta tanks and in some scapes. Never submerged the leaves, though, only the stems. I kind of liked the "rooty" feel it gave the scape. It's the 10g in my about me page. The leaves grew out the back. Looked rather pretty. For betta bowls and tanks, it's a fantastic ammonia remover once established.
Liz