The friendliest place on the web for anyone with an interest in aquariums or fish keeping!
If you have answers, please help by responding to the unanswered posts.
I use a brown colored 4-lb test fishing line. The brown blends in well with the wood I use, so it isn't very obvious. When the plants have attached themselves, it is easy to remove.
You can use the mopani wood (I certainly do), but you should soak it in a bucket for a week or so, changing the water daily, until most of the tannins leach out, otherwise it turns the water brown.
Brown water from tannins isn't necessarily a bad thing. For instance, if you are trying to create a Amazon biotope you will want the tannins for a more realistic result.
Some fish even require tannins in the water to get them to spawn.