Indications.
The term "bloat" or "Malawi bloat" generally renders
images of cichlids swollen to near
apparent bursting and breathing at a rapid rate. A fish observed
in this condition usually succumbs in a short period of time.
Bloat has been related to internal parasitic infections, bacterial
infections, feed, and water quality. These observations suggest
that bloat itself is not a disease, but rather a symptom of a
variety of disease and water quality related problems, each with their
own possible remedy. The observation that bloated fish often
succumb quickly suggests that these problems must be addressed prior to
the fish reaching that condition.
Physiology.
The physiology of freshwater fish offers insight into the possible
mechanism for bloat in cichlid fish. The tissue of freshwater
fish is hypertonic compared to the surrounding water. This
results from internal tissues having a higher ion concentration than the
water around the fish. This creates osmotic pressure and causes
freshwater fish to gain water by diffusion. Freshwater fishes combat osmotic
pressure by producing dilute urine and actively
transport mineral ions from the surrounding water to compensate for
those lost via the urine and diffusion from the gills. (Note:
marine fish have the reverse problem where tissues are hypotonic
compared to surrounding water and they must ingest large volumes of
water and actively excrete mineral ions). This water balance
mechanism is called osmoregulation. The ability to osmoregulate is essential to the well-being of fish and allows fish to
tolerate a range of water quality conditions by maintaining a constant
(homeostatic) internal environment. A general breakdown in osmoregulation due to
disease, water quality, etc.., may be responsible for the bloated
condition that results from excess water accumulation in tissues. It
intuitively follows that fish in this condition often rapidly succumb
due to loss of homeostasis (the constant internal environment), essential to carrying
out metabolism and other life activities.
Tropheus
spp. and Malawi mbuna are considered high risk for developing bloat
Treatment.
Diagnosing the
underlying cause responsible for bloat is critical in determining the proper
treatment. Disease, in many cases, has been identified as a leading
cause of bloat. Parasitic organisms generally multiply rapidly and
will attack more than one fish in a closed system. Preventing
parasitic infections requires quarantine and observation of any new
specimens and perhaps prophylactic treatment. Be forewarned
compounds found effective in treating parasites (e.g. formalin, copper
compounds) are toxic to all aquatic life and work by killing parasites at lower
concentrations than those that would harm the host fish. Wild caught
fish are more likely to carry parasites and should be quarantined and
observed for external as well as evidence of internal parasitic
infections. Bloat in cichlids has been related to a gastrointestinal
infection by parasites (Hexamita spp. and Cyrptobia iubilans) and
bacteria (Aeromonas hydrophilia) (Francis-Floyd 99). Bacterial infections in
otherwise healthy cichlid aquariums are probably more rare. Bacteria
(both opportunistic and obligate pathogenic) must first defeat the fish's immune
system in order to survive and multiply. Fish stressed due to other
causes (parasitic infection, water quality, aggression) are more likely to
contract bacterial infections. A variety of antibiotics are
indicated to treat specific types of bacteria. Separation of the
affected fish is probably indicated to prevent non-infected fish from
contracting the disease. Water quality should be closely monitored
since antibiotics may disrupt nitrifying bacteria. Any equipment associated
with the aquarium (e.g. nets, decorations) should also be disinfected
prior to use to prevent contamination. Poor water
quality should not be overlooked as an underlying cause for bloat or
disease. Water quality can rapidly deteriorate in closed systems,
particularly at the high densities and feeding rates commonly observed in
cichlid aquariums. Poor water quality increases stress on fish and
allows opportunistic infection to occur. Prevention of degraded
water quality is the easiest and least expensive treatment, and a regular
-I would recommend weekly- schedule of water changes should be strictly
adhered to. Many feed related issues suggested to result in
bloat may possibly be explained by poor water quality and a buildup of
metabolites. Again, strict adherence in maintaining optimal water
quality will prevent many problems. Aggression may be another cause of bloat in an
otherwise healthy cichlid aquarium. Repeated aggressive attacks on a
particular fish may cause such damage that the ability to osmoregulate
is lost, resulting in bloat. I have observed this in a group of P.
demasoni where a sub-dominate male was repeatedly attacked and
subsequently developed bloat and was unable to be saved. In summary, bloat in cichlids may
result from diminished capacity to osmoregulate and be symptomatic
of a variety of factors rather than a single condition. This makes
diagnosing the underlying cause essential in determining the correct
choice for treatment.
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