Malawi bloat is one of the most common diseases in Malawi cichlid tanks and it is also one of the most mysterious. There is no clear consensus regarding what is causing this disease, some think it is caused by a parasite while others believe the disease is the result of a bacterium. The former theory (parasites) seems to be gaining ground nowadays.
Despite its name, the disease can occur in other fish than Malawi cichlids. (But it is usually only found in African cichlids.) Herbivores are particularly prone to Malawi bloat. The symptom of Malawi bloat includes loss of appetite, a swollen abdomen, rapid breathing, and white thin feces. The fish will also often become more reclusive. It should however be noted that not eating and being reclusive can be signs that a female is carrying eggs or fry in her mouth if the species is a mouth brooder.
If the disease is allowed to progress secondary symptoms might appear such as skin ulcerations and red marks around the anus. It is very hard to save a fish that displays these secondary symptoms and they usually die within 1-3 days. The cause of Malawi bloat is as I mentioned earlier debated but the theory that it is a parasite, a protozoal parasite to be exact, that is causing this disease seems to be gaining ground.
According to this theory this parasite always live in the intestine of these Cichlids and if the Cichlids get weakened by stress or other factors this parasite can multiply out of control and block the intestine causing the bloating. When their numbers grow even larger they become intrusive and start creating holes in the fish damaging its organs. It is not 100% determined whether this disease is contagious or not. As long as there is no final evidence that it is not, I recommend always treating it as contagious.
The disease can have several different causes of which I believe improper diet probably is the most common. Malawi and other herbivorous cichlids have long intestines. (These long intestines make it possible for the fish to get the nutrition it needs from its herbivore diet.) This means that their digestive system can not handle the high protein foods that they often are feed in aquariums very well. This causes irritation and stress that can give this disease the foothold it needs to develop.
Other common causes for this disease includes poor water quality, over feeding, salt in the water, and a poor environment with too few hiding places. Salt is sometimes used in rift lake aquarium in an attempt to recreate their natural environment, but the truth is that salt do not recreate the natural environment. If you want to mimic their natural habitat you should add calcium and magnesium to the water, not salt.
Treating Malawi Bloat
If you see signs of this disease you should start treatment immediately. You should also try to correct whatever might have caused the disease. Carry out a 30% water change, increase aeration, and take a closer look at the diet (adjust if necessary). The most effective treatments for Malawi bloat are Metronidazole and Clout. Clout is usually more effective and gives your fish a better chance of recovery as Metronidazole sometimes only prevent spread of the disease and don't always help already sick fish.
Clout does however have the downside that it colors your water blue. It will also color the silica in your tank, as well as any and all tubes etc. Move any catfish you might have in the tank to another holding tank before starting the treatment as they might be injured by the meds used. If only a single fish is sick, you might want to consider moving it to a hospital tank and do the treatment there. If several fish is sick, it might be best to treat the entire tank as other fish might be infected as well and just haven't started to show symptoms yet.
The earlier the disease is treated, the easier it is to save your fish. If the disease has progressed too far fish only seldom recover. Adding some Epson salt to the tank can also be a good idea as this might help reduce the bloating a little improving the chances of recovery. Turning of the light can also help improve their chances of recovery as it makes the fish less stressed during the recuperation time.