Nice pictures. I had a big aquarium with malawi-ciklids before, i like.
How is the diving in lake Malawi? How is it for tourists?
To be blunt, I wouldn't make a special trip here just for the diving. On the upside, it's warm water, fresh water, very little (if any) current, all boat diving, laid back crews, sunshine, friendly people, etc... And if you had cichlids in an aquarium, it might be interesting for you. But, the lake is basically catfish, cichlids, and rocks. Visibility can be hit or miss and God help you if there's a medical emergency. Also, tourist facilities tend to cater to very high end or very low end. And even those are not up to international standards. Only about 10%-20% of the country has electricity and blackouts are frequent (and routinely last 8-12 hours). Your lodging may have aircon or fan, but not if they are on generator, which is a luxury in and of itself. We are really, really off the beaten path.
As far as I know there are five dive ops in the country spread out in four locations, only one of which has nitrox (and the only qualified gas blender there just left the country). They are all small operations and mostly do discovery dives. I've only twice seen someone else with their own gear in 18 months of diving here every other month or so.
If you're here for a safari or visiting friends or doing NGO work or doing something else, then yes, go diving--if for nothing else the uniqueness. But there are world class destinations near us (Mozambique and South Africa come to mind) which are MUCH better set up.