Oscars
by Bruce Taylor
From Aqua Scoop, March 2002, Gold Coast Aquarium Society, Australia
Aquarticles
Oscars are big fish! They are a perennial favorite amongst hobbyists and neophytes
alike. So much so, that for many inexperienced fishy people, any BIG fish will be referred
to as an "Oscar."
Originally (in the early 1800's) Oscars were known by the scientific name, Lobotes
ocellatus. The species is now known as Astronatus ocellatus The Astronatus
means being marked with a star on the back, ocellatus means bearing an ocellated
marking or eye spot.
As stated, Oscars are big fish. They can grow up to 35 cm in length, although this is
extremely rare, with most aquarium specimens reaching a maximum length of 25 cm or
thereabouts. Housing Oscars is a chore within itself; they should be kept in a tank no
smaller than 3' by 18" by 18". This will give them room to move (a bit)
and allow them to grow (a bit). If you want to achieve the maximum growth potential for
these fish, then house them in a big tank with plenty of swimming space and good
filtration. They are messy fish and require good filtration in order to do well.
Water conditions are vitally important if you want your Oscars to thrive, and
especially so if you want them to breed. Oscars need a lot of water changes. While they
will cope for a while with poor conditions, sooner or later they will become
hypersensitive to poor water quality and then become susceptible to all sorts of diseases
and problems. The most notable problem for Oscars is hole in the head. I believe that hole
in the head is similar to lateral line erosion seen in marine fish and is primarily due to
poor water conditions and the lack of vitamin C. Parasites in the gut can also lead to
vitamin C deficiencies and subsequently hole in the head. In other cases, hexamita may be
the culprit.
Keeping a salt level in the water seems to be essential part of Oscar keeping. The
addition of salt when a pair of Oscars has a spawning seems to ensure a greater hatch rate
for the eggs.
Feeding Oscars is not difficult, but can sometimes be fraught with frustration. They
will eat anything from live fish to flake food, but more often than not they will try to
train their keeper to provide them with their favorite food by refusing to eat other
offerings until the "right" food is given. Do not fall into this trap! Offer the
favorite, but stick to a wide diet of all food types. Feeding flakes and pellets can be
messy as much as of the intake of food is rapidly expelled out of the gills in a shower of
small particles, thus the need for massive water changes and a good filtration system.
Perhaps the most endearing thing about Oscars is their personality. Oscars are the
closest thing you will get to a puppy. They will often relate to the owner and the
exclusion of everyone else. They are also like a two year old in that they will sulk at
things not going their way. It is not unusual for Oscars, unhappy about something, to lie
on their side on the bottom of the tank until they feel they are getting things their own
way again. They will unmercifully harass and bully weaker and smaller fish, but will often
wimp out against opponents of similar size and nature rather than stand up to them.
Sexing Oscars is an art unto itself; some books will tell you that it is all in the
colouration or patterns. The easiest way is to buy a group of young Oscars and grow them
up and let nature take care of sexing them. The theory is that if you buy six or more
juveniles then mathematical probability says that you should get a pair out of them. This
is fine if you want to wait, as Oscars need to be about 18 months old and 6-8 inches
before they are sexually mature. If you need a pair in a hurry, a way of sexing them is to
compare breeding tubes. These of the male will be pointier, while the female's is shorter
and broader. But you still need a number of fish to compare.
A sign that Oscars are ready to breed is that they will begin clearing a site, or dig a
hole for the eggs. Both male and female will do this. Although the fish are not
necessarily monogamous, they both share the housekeeping, and they protect and raise the
fry. Aggression can increase when they are spawning. The eggs will take about four days to
hatch and the fry can be taken away and reared separately. Feeding the fry takes an
enormous amount of baby brine shrimp, followed by beef heart, pellets and flakes as they
grow quickly.
While not for the beginner, the Oscar provides an entertaining addition to the fold. I
imagine that most aquarists have at some time or another kept an Oscar!
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