I tried anubias and java fern in my mbuna tank for 2 weeks now. My fishes got 'frightened' initially when they saw 2 greeny stuff 'intruding' their territories.
I have since removed the plants. I personally think that if you have already got fishes in the tank, getting them used to the new addition to their environment is important.
BTW, my anubias didn't do that well in the mbuna tank since I have crushed corals as substrate and the water is quite hard as well.