Astronotus ocellatus, also known as the Oscar, quite possibly one of the most personable fish within the hobby.


  Water Dogs! A crash course in keeping Oscar Cichlids
Astronotus ocellatus, also known as the Oscar, is a fresh water species which is a member of the Cichlid family. Wild Oscars are native to the Amazon River basin (as well as the Orinoco and Paraguay basins) in South America. In their natural environment Oscars are typically found in slow moving, whitewater to blackwater environments and can be found taking cover around and within submerged trees, roots, rocks, vegetation and driftwood.

Oscars are one of the hardiest and most popular Cichlids in the hobby and they can learn to distinguish their owner(s) from strangers as well as associate them with food. Oscars are very intelligent and will develop and display unique and interesting personalities. In addition to their constant "begging" for food, Oscars can also be trained to eat from their owner's hand; which is why they are sometimes referred to as river or water dogs.
  Choosing your Oscar:
The original species of Astronotus ocellatus is the Wild Oscar (also referred to as the Common Oscar); the Wild Oscar is the only Oscar that can be found in it's natural habitat in the wild (aside from various "pets" that have been released in ponds, lakes, canals, and rivers within sub-tropical or tropical environments). All other varieties of the Oscar have been bred exclusively for the aquarium trade, including varieties with red marbling, albino, leucistic, and xanthistic. Red Oscars, Tiger Oscars, Red Tiger Oscars, Red Lutino Oscars, Lemon Oscars, Platinum Oscars, Gold Oscars, Copper Oscars, Albino Tiger Oscars, Albino Red Oscars... the list goes on. There are also veil-tail (long-finned) versions of all the various forms in the aquarium trade, but it's not recommended that they be kept with other Oscars or aggressive Cichlids; as their fins are delicate and are prone to damage, which can cause various fin diseases or infections.
When choosing an Oscar, make sure to examine it closely before you decide to purchase it. Keep an eye out for the ones that are very alert and active. Don't choose one that is acting completely different from the rest, seems to be lethargic or just happens to be lying on the bottom of the tank pouting or possibly not feeling too well. A healthy Oscar is always alert and looking for food.
If you plan to purchase a mature Oscar, keep an eye out for any pitting or holes that may have devleoped on it's head; It's a sure sign of Hole in the Head Disease.
Also make sure your future pet Oscar does not have any small white spots (similar to tiny grains of salt) on it as it's a sure sign that it has been infected by Ick (an Ichthyophthirius multifilis parasite).

  So, you brought home a new Oscar for your tank...
The water chemistry at a fish store is usually fairly neutral at a pH of around 7.0 and the GH and KH can very greatly, not to mention that it can also contain various nasty parasites. When introducing a new Oscar to a tank, you can't go wrong with the "drip" method as even baby Oscars have been known to tear little holes in the store bags and nobody wants fish store water in their tanks.
Carefully empty the contents of the bag (including the water) into a container. Take some airline tubing and set up a siphon drip line from the target aquarium to the container with your new Oscar. If you don't have an airline control valve handy, you can tie a couple loose knots in the airline to control the rate of water flow (it's also recommended that you secure the airline tubing in place with an airline holder or some other method). Start a siphon by sucking on the end of the airline tubing you'll be placing into the container. When water begins flowing through the tubing, it's time to adjust the drip (either by adjusting the control valve or tightening one or both of the knots) to a rate of 2-4 drips per second. When the amount of water in the bucket doubles, empty half of it and start the drip again until the volume doubles again. Repeat this process for about one hour and then your new Oscar is ready to be netted and moved to your target aquarium.
New Oscars will often pout. If your new Oscar swims to the bottom of the tank and lays on one side, looking up at you with an untrusting eye, don't panic, it may just be a little stressed and will soon get over it and snap into action, exploring its new home. Current, resident Oscars consider new Oscars a threat as well as intruders in their territory. The bigger the Oscars are, the bigger the fight can be. They will sort things out, but there maybe be a few bruises and hurt feelings in the process.

  In the Aquarium:
Oscars are excellent for breaking in a beginning Cichlid hobbyist as they are a very hardy species and their owner(s) will learn a lot about the care and habits of predatory fish, water conditions, filtration and how much fun it can be to have a Cichlid tank. Oscars can live for 12 to 16 years and it's important to understand that Oscars are a long-term commitment.
In their natural environment, Oscars can be found in acidic blackwater conditions as well as neutral whitewater conditions with a pH anywhere from 4.5 to 7.5. In an aquarium environment, Oscars will thrive in conditions with a pH ranging from 5.0 to 7.0 and a temperature between 74 degrees F to 84 degrees F; When it comes to water hardness, the GH should be around 3 to 7 and the KH ranging from 2 to 4.
Oscars are one of the fastest growing aquarium fish in the hobby and baby Oscars are usually sold at the fish store at around one to two inches long. Those babies will easily gain one inch a month for the first eight months. Expect those babies to be seven or eight inches by the time they are a year old. Ideally, a single Oscar should be kept in a tank that is no less than 75 gallons and a 110-125 gallon tank is recommended for two. Oscars are greedy, big and messy eaters and produce a considerable biological load within their environment. Therefore, the two most vital components for Oscars are tank size and filtration; a large tank with an efficient amount of quality filtration will play a vital role in keeping your Oscar(s) happy and healthy.
Oscars love to decorate and will rearrange their environment to their liking by digging large pits within the substrate and relocating rocks and other objects (including submersed heaters and thermometers). Oscars are very powerful fish and can and will move almost anything in the tank aside from large pieces of driftwood. As far as live plants go, Amazon and various Swords are recommended as they will grow powerful root structures and may be too difficult to move. Most other live plants will either be uprooted or shredded. Oscars have also been known to actually break heaters, filter intakes, under-gravel filter stems, and floating thermometers. Sometimes the wreckage is from an accident, other times it's on purpose as the Oscar was using that floating thermometer as a toy. If you want to give your Oscars a toy to play with, occasionally throw a clean ping-pong ball into the tank and enjoy the show.

Oscars are the beginner's species of New World Cichlids and an introduction to the more aggressive species, but despite their size (average of 14 inches in the aquarium), predatory nature, and the fact that Oscars like to play rough, they are not considered to be an aggressive species themselves, as long as their tank mates are too large to be mistaken for food (an Oscar will eat any fish that can fit its mouth). Oscars mainly show signs of aggression when they are feeding, getting ready to breed, arguing over territory, or when they want some exercise.
Unlike the more aggressive Cichlids, Oscars are not known to incessantly bully or terrorize their tank mates for no apparent reason. First-time Oscar owners often panic when they see their first Oscar argument. Expect occasional arguments, that's what Oscars do; Oscars like to test their tank mates. They may try and bully other fish once in a while, but will not usually persist if the other fish can get out of their way fast enough. In addition to a nip here and a bite there, Oscars will fight and test each others strength by jaw or lip locking and will wrestle and tug on each other, which can sometimes lead to some nasty scrapes and abrasions. Don't immediately separate Oscars or tank mates when you see aggressive behavior. Observe them for a little while and see how it goes. It should become apparent if it's a short argument, a change of command, a breeding ritual, or an all out war. MelaFix is an excellent, natural medication that promotes quick tissue regeneration and wound healing; it’s highly recommended for any Cichlid tank.
If you end up with enough room for some tank mates to keep your Oscar(s) company, be very wary of small Catfish and small Plecos. An Oscar will eat any fish that it can fit in its mouth and Plecos and catfish have sharp, strong barbs that can kill the Oscar that gets one stuck in its mouth or throat. Catfish and Plecos can make great tank mates, but be sure to get them large enough so that an Oscar can't fit them in it's mouth. Silver Dollars and various Geophagus species also make great tank mates as they are fairly peaceful and very tough. It's possible to add other Cichlids as tank mates, but there will be arguments for sure. There have been tanks housing Oscars, Pike, Jack Dempseys, Arowana, Peacock Bass, and Managuense, but it's hit or miss and only recommended that an experienced hobbyist makes the attempt.

  Feeding Oscars:
The first thing that should be noted is that Oscars require vitamin C and will develop health problems in its absence.
Oscars are omnivorous (more accurately, facultative piscivores); They love live foods and enjoy the chase (your live plants won't). Feeding Oscars live fish can make them more aggressive (some hobbyists like this idea) and most readily available live feeders have little to no nutritional value. Goldfish and Rosy Red minnows should be taken out of the mix completely due to being extremely fatty and rich in a chemical called thiaminase (an enzyme that destroys the essential nutrient thiamine, also known as vitamin B1). In addition to being a catalyst for vitamin deficiency, Goldfish and Rosy Reds also have the ability to introduce some nasty parasites and bacteria into the aquarium which can cause a number of different diseases (Ick and velvet are extremely easily transmitted between feeder fish).
Baby Oscars (until they reach 1 month) should be fed 3 times a day with live, frozen, or freeze-dried: Brine shrimp, blood worms, black worms, tubifex worms, and/or small shreds of frozen krill. Once the Oscars are a little older they should also be given beef heart, white cloud minnows, ghost shrimp (gut loaded), and river shrimp, as well as mealworms and small Cichlid pellets. As the Oscars get more mature (5+ inches), they should be fed 2 times a day with, earthworms, frozen krill, shrimp, medium Cichlid pellets, live crickets, peas, lettuce, pieces of cooked or fresh fish, and minnows.
When the Oscars grow even larger (8+ inches), they should be fed 1 to 2 times a day (2 if you give in to their begging or want them to reach full size quickly) with all of the previously mentioned foods in addition to large Cichlid pellets and cooked mussels as well as an occasional small frog, large tadpole, or crayfish. Feed your Oscars a wide variety of the foods listed and they will have all the nutrition they could ever need.

  Oscar Health:
Home aquariums contain insignificant volumes of water compared to an Oscar's natural environment. In the wild, Oscars rarely encounter excess amounts of ammonia, nitrate, nitrite, and harmful organisms and they are much more resistant to infection due to the relatively low concentration of harmful chemicals and organisms in such a massive volume of water. Although, in a home aquarium, biological waste can pollute the water extremely fast and if left unchecked, water chemistry can become extremely toxic to Oscars and harmful organisms can multiply exponentially, infecting them with or introducing them to disease and serious illness. However, if Oscars are well cared for and their water chemistry is maintained at optimal levels, Oscars can easily resist any effects from harmful organisms in very low or nonexistent concentrations.
Water changes (at least 25%) should be carried out every 2 weeks (or more or less frequently, depending how efficient your aquarium filtration is). Oscars are very hardy fish, but they are also big and messy eaters and eventually they will have health problems if their water chemistry is not maintained; filthy water is usually where "one-eyed" Oscars come from as well as Oscars that have developed HITH (Hole-in-the-Head) disease.
There are a number of different freshwater fish diseases and parasitic infestations out there, but the following two are the most common with Oscars:
Hole-in-the-Head Disease (HITH): Oscars are known to be susceptible to a nasty disease called Hole-in-the-Head; Other common names for this disease are Freshwater Head and Lateral Line Erosion (FHLLE) and Hexamita Disease. Nobody really knows the true cause of this disease, and although it can be fatal, if treated early and properly your Oscar can survive (aside from permanent scarring). Signs of HITH include pitted lesions on the head and lateral line. HITH will be mild at first, but if not treated, pitting will become more intense and secondary bacterial and fungal infections can develop, which will eventually lead to a severe infection and the Oscar will become systemically ill with eventual loss of appetite and life. HITH can be treated with an antibiotic called metronidazole, or a combination of MelaFix and PimaFix can be used.
Ich (Ichthyophthirius multifilis): Also referred to as White Spot, is a burrowing parasitic infestation that causes the skin of the fish to swell and produce white cysts that can be observed as small white spots covering your Oscar to varying degrees. An early symptom (before the spots are visible) is usually when your Oscars continuously scratch themselves on rocks, substrate and driftwood. In the more advanced stages, the Oscar will become lethargic and will eventually develop redness or bloody streaks across its body. Although the infestation itself is similar to a human skin infection, it can be the death of an Oscar with poor nutrition and water conditions.
Ich can be treated by first doing a 25 to 50% water change, then raise your aquarium temperature to 86 degrees F, discontinue any carbon filtration, add a normal dose (listed on the box) of freshwater aquarium salt and obverse the situation for 2 weeks. If things don't clear up, repeat them again and add normal doses of MelaFix and PimaFix as well and observe for another 2 weeks. That should do the trick. One of the best ways to avoid Ich and other parasites is to quarantine new fish in a separate tank for two weeks while performing the full Ich treatment (with MelaFix and PimaFix) before introducing them to your main tank.

One thing that every Oscar owner will have to get used to is that Oscars have a tendency to get cuts and abrasions as well as fin damage once in a while; Either from playing rough with other Oscars or tank mates, or even just bumping into various objects (heaters, driftwood, rocks, filter equipment, etc.) in the tank while chasing food, Oscars seem to always get hurt at some point and it can be quite disturbing for newcomers seeing these injuries for their first time. Although some of these injuries may look rather serious, they are actually superficial wounds and Oscars will quickly heal on their own. Keep their water clean and they will be fine. No medication is necessary, but if you want to help speed up the healing process you can add a normal dose of MelaFix to the tank to speed up the tissue regeneration process.
  Oscar Breeding:
Oscars are monomorphic and it's almost impossible to sex them (it is impossible to sex young Oscars), but at breeding time you will have a around 4 days to attempt to sex your Oscars; a male's breeding tube can be observed as being small and pointy where the female's egg tube is larger and more oval at the end. Unfortunately, two females will sometimes pair off and lay eggs together and several infertile clutches will eventually let you know that you have two females instead of a breeding pair. Unfertilized eggs are milky white while fertilized eggs are tanish to amber.
A breeding pair of Oscars can be conditioned for spawning by feeding them live food such as freshwater shrimp, minnows, frogs and crayfish. A pair of Oscars will usually test each other with a jaw/lip-locking, breeding ritual and once they both pass, they may chase each other around for a little while and then they will begin cleaning off rocks in the aquarium. At this time it's recommended to provide them with a large slab of slate where the female can lay her eggs as Oscars will not lay eggs on substrate. Once the Oscars clean off the area, the female will lay her eggs (up to 1000) and the male will fertilize them. While Oscars are breeding, they are extremely protective of their area and no other fish will be allowed near it.
The eggs will hatch in 3 to 5 days and the fry will look like a wiggling mass with tails, attached to the slate; as they start to absorb their yolk sacs, they will eventually fall to the substrate in a sticky blob. Once the fry are done with their yolk sacs (around 4 days), they will begin swimming on their own and will be ready to consume gargantuan quantities of baby brine shrimp (their water will need to be changed often). Because Oscars will care for their eggs and practice brood care for their newly hatched fry, it is safe to leave the fry with their parents for about a month, after which they should be relocated to another tank. Some breeders will move the slate and attached eggs to a different tank (using the same water) after they are fertilized, for fear of the parents may eat them. If the slate is relocated into another tank, the eggs will hatch on their own, but beware of Oscar attacks while trying to remove their eggs.

  In conclusion:
Oscars can be a lot of fun and are a great introduction to predatory fishkeeping. They are truly a species that will bring a lot of personality and activity to any freshwater Cichlid aquarium. Remember to keep their water clean and they will thrive and offer years of enjoyment and excitement for the beginner to intermediate hobbyist.

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