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A General Overview of the Oscar Fish - Astronotus ocellatus
Scientific Name: Astronotus ocellatus (invalid/outdated synonyms: Lobotes ocellatus, Cychla rubroocellata, Acara compressus, Acara hyposticta, Astronotus ocellatus zebra, and Astronotus orbiculatus)
Common Names: Oscar Fish, Velvet Cichlid, Marbled Cichlid, or any number of color/pattern variations + Oscar (Tiger Oscar, Red Oscar, Common Oscar, Albino Oscar, Lutino Oscar, Wild Type Oscar)
Size: 12-16 inches standard length (SL) and up to 3.5 pounds (though closer to 12+ inches SL is more typical in a home aquarium). When young, can grow at the impressive rate of up to 1+ inches per month. Don't be fooled by their small purchase size and get a small tank thinking you will have time to upgrade later; this is a common mistake.
Origin: Natively found in South America - Amazon and Orinoco River Basins - Argentina, Brazil, Colombia, French Guiana, Paraguay, Peru, Uruguay, and Venezuela
Water Parameters: Tolerates pH between 6-8, a General Hardness of anywhere from 5-19 dH, and a water temperature of about 72°F - 78°F. While this is a wide range, this doesn't mean your water can fluctuate between these extremes. Stability must be maintained or else it is extremely detrimental and sometimes fatal to the fish. Oscars are benthopelagic, meaning they swim and feed in open waters as well as on the bottom. They are typically found in shallower, slower moving waters, with sand or mud bottoms.
Food Items: Insects and insect larvae, crustaceans and other invertebrates (such as crayfish and worms), fish, and various plant matter. However, being opportunistic, just about anything that will fit in their mouth is fair game. This nature causes them to always act hungry, even if they are being well or even overfed. Overfeeding and resulting health issues is fairly common in the hobby because of this.
Longevity: Oscars can live for well over a decade. Success with these fish is measured in years, not months. These fish are a long term commitment that should not be taken lightly.
Temperament: Oscars are mildly aggressive. They have a rumored vicious nature, but that just isn't the case. This rumor is derived from the fact that they are many times willing to attempt to eat anything in the tank they think will fit in their mouth. In all reality, the are pretty mellow compared to other cichlids, and are many times bullied by other more aggressive cichlid tankmates. They are territorial though, and a breeding pair may become highly aggressive towards tankmates when spawning. Also, providing too small of an aquarium can cause two Oscars in the same tank to constantly fight, sometimes to the point of being fatal.
A Brief Overview: Oscars are extremely intelligent fish capable of being conditioned to do many little tricks. They quickly learn to recognizing those that feed them and reacting accordingly (usually begging for food). They have a unique presence, intelligence, and attitude that makes owning them a true joy to those that love them. This combined with the fact that Oscar can live just as long as a dog makes them more like a pet than most other fish could ever be. Each fish seems to be an individual with its own unique nuances, making owning one of these fish even more appealing.
Oscars are hardy fish for the most part and can take a lot of abuse without displaying outward symptoms of many health problems. Just because you can't tell there are problems doesn't necessarily mean the fish are healthy by any means. This unfortunately leads many people to believe that they really do not need much care, when that is not the case at all. They are actually fairly susceptible to poor water quality and nutritional deficiencies. Many times these sensitivities will express themselves in the form of Hole in the Head/Lateral Line Erosion (HITH/LLE). This is why it is extremely important to replicate the variety found in their natural diet and even supplement with vitamins when necessary.
Many people feed an unbalanced diet that contributes to these nutritional deficiencies. Fish stores typically promote feeding solely of live feeder fish. There are two problems with this. First of all, only feeding fish can lead to nutritional deficiencies from lack of variation. Oscars are not piscivores (only eat fish), and have evolved to consume a wide diversity of foods, and really need to do so to be healthy. In the wild they typically eat more insects and crustaceans, but since they are opportunistic, they typically won't pass up anything that could be a possible meal. Secondly, live feeder fish from a fish store is almost a sure way to introduce parasites and other various pathogens into your tank that are harmful to your fish.
Other individuals only feed beefheart. Again, this can lead to nutritional deficiencies if it is the only or primary food given. However, another more serious problem can arise from the fact that fish are only capable of processing so much fat, especially saturated or or hard fats found in higher concentrations in most tissues of warm blooded animals. Luckily beefheart is relatively leaner that other beef (except liver), and in very sparing amounts feeding would be OK, however the tendency of the home aquarist is to overfeed with such a product can be a fatal mistake. Uncooked it is still extremely higher in saturated fat than other natural foods. The long term results of overfeeding saturated fats can be deadly, as this can attribute to what is commonly called fatty liver disease. This is a swelling of the liver and/or other internal organs. Even worse is that there are typically no external symptoms of this condition, right up until the point the fish just dies and an autopsy reveals the cause. This is an extremely likely cause of death for many Oscars that unexpectedly die sooner than 10 years that have otherwise been very well cared for. It is so easy to avoid potential problems like this, yet so many people fail to provide the necessary diet Oscars require. Providing a wide variety of foods, in the correct amounts, while feeding a staple of a quality cichlid pellet goes a long ways towards ensuring the health of your Oscar.
A lot of individuals also don't realize just how large these fish get. They can easily grow to a length that exceeds the width of a standard 55-gallon aquarium, and do so very quickly! Because of their mass, they can put an extraordinary bioload on an aquarium, so plenty of water to dilute waste and massive filtration is critical. Large water changes are also required to keep down nitrates. The myth of 1" per gallon just doesn't apply, if that happens to be crossing your mind right now. Think about it; would 12 1" guppies come anywhere near the mass of a single 12" Oscar? Not even close. This is a common misconception which leads to the demise of many Oscars every year. To further complicate things, Oscars are somewhat territorial, and too limited of a space can sometimes cause two Oscars to fight to the point of being fatal.
New Oscar Owner Information Pack - Oscar Care Checklist
For more information about Oscar care (tank setup, necessary equipment, etc), please read the