In my experience cichlids from Lake Victoria and Lake Malawi make
perfect tankmates due to their very similiar requirements. I have 48
tanks and almost every one of them I successfully keep fish from both
lakes in. What you probably have is a case of "Malawi Bloat". Both
Victorians and Malawians do very well in pretty much any time of water
but what you REALLY need to worry about is their DIET. Many cichlids
form specialized feeding habits in the wild and require certain foods
or the natural parasites that are always present in their digestive
track can get out of control. Then, with a reduced immune system from
improper feeding the fish develops this disease that blocks their
digestive track and that is why they have the sunken bellies(from not
being able to eat). The best thing you can do is remove the cichlids
and put them in a heated and biologically cycled tank and add a
handful(literally) of 50% epsom salt/50% canning-pickling salt(only w/
no additives) mixture and do 50% water changes every other day and hope
it does the trick. During this time DO NOT feed. You can also get an
anti-biotic at Jehmco.com called Metronidazole and treat exactly as
directions describe but don't get your hands in the water as
overexposure to antibotics can lead to ineffectiveness if you ever need
them... Hope this helps.
James
http://www.africancichlidcentral.com