I've read in many places where people have had issues with Mopani, too - sometimes right away, sometimes not for quite some time! Of course many others have never had an issue with it, so it is generally considered to be aquarium safe, and one of the more common ones to find for sale. I definitely keep a close eye on ANY wood that I put into my tank, at least at first. Fungus is a risk you'll take with any wood, even though it *seems* to be more commonly reported with Mopani (that I've seen, anyway). From all I've read, *most* of the time, the fungus/mold that develops is harmless, and will go away itself in a short time - but there's always the oddball toxic stuff that gets reported and gives me the shivers! I've never personally used anything but Manzanita in my tanks, and always pulled and boiled and scrubbed on the few occasions I saw filmy white stuff forming. Better safe than sorry! O.O
I always boil driftwood (if possible), or at least pre-soak it before putting it in the tank - though that's no guarantee you won't have issues down the road. Pre soaking will give it a good cleaning, waterlog it so it sinks right away, and remove some of the tannins from the piece. Tannins are great for softening water, and enough of them will turn the tank a pretty tea color - a lot of people use driftwood with that goal in mind. Harder woods, like Manzanita have less tannins than softer stuff, like Mopani (which is one reason why I chose this type, my water is soft enough already). Also a good idea to give it a nice scrub with a clean scrub-brush to remove any leftover bark or debris that may be on it.
Malasian driftwood is also a very good choice for the tank, and commonly available in shops.
Driftwood is so pretty (to me!) and I think it looks fantastic underwater! Happy shopping! ^.^