Okay let me restate my self there are some tress in the lake but not many as the locals pull it out and use it as fire wood, not enough to where I would use it in a tank as 99.9% of the lake it rock and sand, so me saying there "arnt" any tress is wrong but there isn't enough IMO to use it to bring a "natural" look to a malawi tank unless your doing a species where they are found around the the very few trees there are in and around the lake.
PS OP I like your tank dont get me wrong its just most of malawi is rock and sand, im a bit of a prude so dont let my opinion sway how you feel about your tank cause it looks good.