The Otocinclus catfish
is a staple for most of us with
planted tanks. Many hobbyists
report only 50-percent success
rates with these fish, and some people say
that Otocinclus are so sensitive that even
pointing at them could kill them off in large
numbers. I’ve never had this issue, and on
the contrary, would suggest that a low-yield
nuke might only stun them!
Otocinclus are misunderstood fish. Since
they are catfish, people treat them as such;
they are placed into tanks with improper
conditions, unsuitable tankmates, and not
enough proper food to eat. This often
results in them dropping dead or being
eaten in a short matter of time.
Otocinclus at the Store
For some reason, these guys do not
receive the best treatment on their way to
your local fish store (LFS). Many times,
my LFS has received orders totally dead
on arrival. Typically, they are starving and
maximally stressed, and often do not last 24
hours. So it is a good idea to purchase your
Otocinclus a minimum of four days after
they arrive at the LFS, as the unhealthy
individuals generally do not last this long.
Buying on the first day of shipment is really
not a good idea at all. Even when I special
order Otocinclus, I pay up front and ask
they be held for five days before I come
and get them. I also order a few extra, as
die-offs always happen in the first couple
Selecting Your Specimens
The selection process should depend
on six traits. After the four-day waiting
period, if they are healthy, the remaining
Otocinclus should be chosen based on
ACTIVELY SEEKING FOOD
Otos that stay motionless for long
periods of time are still showing signs
of stress and/or mistreatment. Usually if
the net goes into the tank and the fish
moves, but not fast, it is best to avoid
purchasing the specimen—it may be a
straggler from the initial die-off batch.
Otocinclus actively seek food a lot.
Their mouths are always working
on some object, and their bodies just
move behind. Sometimes I wonder if
the mouth of the oto controls the body.
WITH OTHER OTOS
Otocinclus are extremely social fish. Large
schools have a complex hierarchy in which
males generally dominate the scene. Since
they actively seek the company of their
own kind, you should have a minimum of
a group of three, with larger numbers for
ultimate security. Watching a large school
( 12 or more individuals) move in unison
as it searches for food is a unique sight. A
lone Otocinclus in the corner of the tank is
often not a good sign, so avoid this one as
well. The antisocial Otocinclus is not going
to fare well.
NO CLAMPED FINS
Otocinclus usually have their dorsal and
caudal fins erect, even when eating and
moving around. An individual with both of
these clamped against its body is saying, “I’m
really not feeling too good—avoid me.”
Healthy fish will have no red marks
or any surface anomalies such as cuts or
wounds. Red gill plate covers, wounds,
lesions, abnormal swelling, or any
symptoms of common maladies should
be avoided. In fact, you should avoid
the entire tank. Chances usually are
if one has it, then others will as well.
The fish you choose should have
well-rounded bellies without a caved-in
appearance. A well-fed Otocinclus is not
only a healthy one, but a happy one.
They should have a slight bulge in their
belly area (a little more on the ladies)
to indicate happy, well-fed, healthy
individuals. Those with the caved-in,
sunken appearance in their bellies also
show a dingy white color, as opposed to a
much brighter white in a healthy specimen.
Not only do you want the fish in the
tank you are buying from to be healthy, but
specimens in neighboring tanks should be
in good shape as well. This is especially
true with a central filtration system or
tanks with dividers separating them into
sections. In these cases, you should look
at the health of the fish in the tank you
are buying from and the adjacent one(s)
attached to it as well.
Oto cats are very social fish, actively seeking the company of their own kind.
Other Buying Notes
No matter what species you purchase, it is
always good to quarantine new selections.
Otocinclus are particularly prone to ich and
dropsy. Also, since Otocinclus are small,
they are more prone to handling damage.
Rough handling, even during netting at
the store, can cause internal damage. For
handling Otocinclus, I avoid catching them
in nets and prefer to use one only to herd
them into a container (usually a plastic
cup). You can then transfer them to a
plastic bag without using the net.
Gender determination is another
consideration. Since you will be selecting
in a store, here are some quick ways to
determine male or female. Males are usually