Bloat is without a doubt one of the most prevalent diseases afflicting aquarium kept African Cichlids. While there is some debate on whether it is parasitic or bacterial in nature, (or a combination of both) most researchers believe it is initially caused by parasites. These parasites, flagellates that normally reside harmlessly in the fish's intestines, increase to harmful numbers due to a lowered immune system caused by stress. Due to it's lowered immune system, the fish also becomes more susceptible to infection, further reducing it's chances of overcoming the initial diagnosis.
"It is not uncommon that the immune defense system is so much reduced that the fish is also infected with a bacterial disease. It may therefore be necessary to combine the metronidazole/dimetridazole treatment with an antibacterial medicine (antibiotic), for example medicines that contain nifurpirinol such as Aqua Furan and Bio Furan."1
The various stressors that lead to bloat are caused by many factors.
The most common is long-term exposure to poor water conditions.
This can be due to infrequent water changes, not enough aeration
(for the nitrifying bacteria), and overfeeding. All three of these
factors lead to elevated nitrate levels in the water. Fish are
very good at fighting off illness but when they are stressed their
immune system weakens leaving them vulnerable to disease, bloat
being one of the most common.
Other causes of stress may include catching fish, transporting them, water changes, sudden changes in water conditions, and aggressive tank mates. A fish that is constantly being chased or is often seen lurking in unusual areas, such as near the top of the tank for bottom dwelling fish, or behind filter intakes and heaters, are often victims of aggression and as such are at a higher risk of developing bloat or another illness due to constant stress.
An improper diet can also lead to bloat. Many cichlids - particularly herbivorous ones - have long intestinal tracts, requiring a relatively longer period of time to digest their food. Consequently, it is quite common for these cichlids to develop intestinal problems. The decomposition of improperly digested, or improperly excreted foods can irritate the intestinal wall, and stress the fish, giving the invasive parasite a foothold. This can often come about when a primarily herbivorous, algae-scraping cichlid (like Tropheus or Pseudotropheus spp.) is fed high protein foods such as bloodworms, or pellet and flake foods containing large quantities of fish meal. Slimy or soft foods, such as brine shrimp, should be avoided and replaced with crunchier foods such as mysis. In light of this information, and experience, it is important to avoid certain foods, and to go light on others. (For a detailed discussion of this topic, see Feeding African Cichlids.)
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