I am having a problem with
my cardinal tetras, which are
hiding in a back corner of the
tank and have gone nearly white, with no
color. All the other fish seem fine. The water
is a little cooler than normal, about 72°F
( 22°C) when it is usually about 80°F ( 27°C).
The indicator light on the heater is on.
Paracheirodon axelrodi, the
cardinal tetra, is a popular
fish that is collected in warm
blackwater streams in Colombia
and Brazil. Captive-raised cardinal tetras
are becoming more available, and even many
wild fish are acclimated to water with higher
pH before they are shipped. The species is
nevertheless considered to be more sensitive
to changing conditions than the other two
Paracheirodon species, the neon and green
The most likely cause for the stress color
and behavior of your tetras is the drop in
temperature. Cardinal tetras like warm
water, and such a dramatic temperature drop
in a short period of time is a change that
they will not like. Check the condition of
your heater and make sure that it is actually
heating the water.
I have three bala sharks.
I just put them into a
new tank and they turned
upside-down straight away and rose to
the top as if they were gasping for air. The
water temperature is fine, but I did not
quarantine them for as long as I should
have. What went wrong?
The bala shark (Balantiocheilos
melanopterus) is a cyprinid
from the Malay peninsula,
Sumatra, and Borneo. This
popular aquarium fish likes to be in schools
and can grow to 14 inches ( 36 cm), so it
requires a large aquarium. The bala shark
is listed as endangered on the IUCN Red
List (a list contributed to by scientists to
raise awareness for species that are at
risk of extinction) due to habitat loss and
overfishing. The species is produced in large
numbers on fish farms in Indonesia, which
is where almost all of them in the aquarium
hobby come from.
The bala shark is a hardy aquarium fish
that can tolerate a wide range of water
conditions, but it is notoriously susceptible
to shock. Many people have experienced
sudden losses when adding new bala sharks
Send your questions about the
freshwater side of the aquarium
hobby to “Q&A,” T.F.H. Publications,
P.O. Box 427, Neptune, NJ 07754,
or submit via email to editor@tfh.
com. For answers to more time-sensitive questions, opinions on your
setup, or just to converse with like-minded members of the aquarium
community, please visit the TFH
Forum at forums.tfhmagazine.com.