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Amazon River basin
Needs 30 gallons. Prefers more.
Tears live plants to shreds
75 to 80o
Loves all foods – especially fish
Likes heaters, snails, and ping pong balls
Needs frequent water changes
Flat piece of slate
Discernible only during spawning
Not every fish has its own Web site on the World Wide Web (plus a French site). If you want to ask a question of other oscar owners, just fire up your computer and wait for the answers. Some may even be correct.
Astronotus ocellatus, better known as Oscar, is an eating machine. Because Oscar is so addicted to eating, you can train him to do tricks. Do not teach him to jump out of the water for food. He already knows how to jump out of the water. Your oscar may jump out and expire while you’re not there. Keep him securely covered.
Reach for Your Salt Shaker. Unfortunately, lots of info on the web is from old books or someone’s experience with one oscar. There’s nothing wrong with anecdotal reports, they’re just limited in their scope. Not every oscar is the same as every other oscar. Similar, but not the same.
Small Oscars. Just a note of caution, those “small oscars” you see for sale are not just “smalls.” Treat them as BABY oscars. In other words, give them BABY foods. Rather then starting them on hard pellets, feed them frozen brine shrimp or other foods preferred by young fishes. Just remember that oscars up to two inches are really babies.
Original Oscars. Normal oscars, which you rarely see these days, start life as cute little black and white fry (looking a lot like baby Jack Dempseys) which quickly grow into dark, bass-resembling predators. Their velvety black and olive bodies are sprinkled with orange “stars” (Astro) on their back (notus). They sport the characteristic “eye” on their tails (ocellatus).
Red Tiger oscars sport the “eye” (ocellatus) on their tails that gives them their Latin name. You won’t see this eye on the reds or on the albinos. You can sometimes spot an “eye” on an albino tiger.
Red Origins. If you wonder where those bright red oscars came from, you need only see a stringer of wild oscars caught in Florida. The crayfish in their diet and other outdoor factors make them beautiful fishes. You can see where selective breeding could easily produce oscars with much more red (and they did). Today’s Red and Red Tiger oscars now originate from concrete vats in Florida and Singapore. You can’t seine them out of the Amazon River.
Red Foods. You bring out the reds in your oscars by feeding them foods with carotene in them:
• Pellets with Carotene
Non-Red Foods. Back in the old days, people used to feed oscars Purina Trout Chow which did not bring out their colors. Or, for color, they would grind up beef heart, spinach, and carrots. Then freeze it in thin slabs. Feed your oscars minnows or plain pellets and you soon get dull-colored fishes. Ditto if you feed them guppies or earthworms. They love them, but none of these bring out their red color. Limit their consumption of non-red foods.
Other Foods. Oscars will eat any fish that will fit (or almost fit) into their mouths. Oscars frequently swim around for hours with a semi-swallowed food fish sticking out in front of them. Will they choke or drown? Not likely. In addition to fish, oscars eat nearly anything edible. They love nightcrawlers, snails, and crayfish.
Baby Foods. Baby oscars eat live, frozen, or freeze-dried:
• Brine Shrimp
• Blood Worms
• Tubifex and Blackworms
Baby oscars also like flies, beef heart, and other frozen foods. As they put on some size, add guppies, white clouds, ghost shrimp, and rosy reds. They will also eat flake foods and small pellets.
Baby Oscar Colors. You buy your bright red baby oscars and take them home. Most soon lose that vibrant red you selected them for. Why? They were juiced in Singapore (or Indonesia, Bangkok, etc) – probably with testosterone or something similar – to bring out their adult coloration. (We can’t use testosterone in our U.S. water, because it makes our arms too hairy -- especially during a full moon.) In your tank, they gradually revert to their true juvenile colors. This is just a phase. They will regain their bright colors again at maturity – about a year later. No matter how many color foods you feed them, the young ones won’t look as colorful as the adults. Oddly enough, many color foods will quickly bring out their blacks and make your oscar darker faster.
Medium Oscars enjoy worms, mealworms, waxworms, plankton, and medium pellets. And, of course, feeder goldfish and rosy reds.
Bigger Oscars go for krill, silversides, grasshoppers, night crawlers, larger feeder goldfish and large pellets.
Sexual Differences. How do you sex oscars? The ones you see laying eggs are females. All bets are off on the others. (Two females may pair off and spawn together.) At breeding time, the male’s breeding tube looks like the writing end of a ball-point pen. The female’s egg tube looks like the other end of the ball-point cartridge. This gives you a four-day window in which to sex them. The French web site calls their sexual differences “inexistante.” You cannot sex young oscars, period.
Big Eaters. The trait that endears oscars to most people is their insatiable appetite. Their gourmandizing begins at an early age and never ends. They remind you of hatchery-raised trout at feeding time. Oscars nearly climb out of their water to get at the food in your hand. A spawn of 500 baby oscars makes the funniest snapping noise at feeding time. The surface just pops with their smacking lips as each strives to be first in line. The “small oscars” sold in shops are actually baby oscars. Baby oscars need baby foods. Many baby oscars fare poorly on flake foods. Give them frozen brine shrimp or other tasty treats for a month or so -- as well as the flakes.
What about Slime? If you fail to make your water changes on a regular basis, your oscar WILL develop a slime coating – from the accumulated filth in his water. His eyes will cloud and actually rot out. One-eyed oscars usually come from dirty water -- rarely from injuries. Forget about antibiotics. When you fall in the pig lot and cut your arm, you need more than a coating of iodine. Change half his water. Add NovAqua. Repeat the process every other day until he returns to normal. Big oscars can stand a great deal of abuse. Unfortunately, filthy water will zap the best of them. It rots their eyes out.
Hole-in-the-Head Disease. Wimpy fish like Discus cannot survive hole-in-the-head disease. If you look at many large oscars, you can see the zit pits in their faces. The Hexamita varmints that cause these scars can easily be treated with Metronidazole. Except for the scars, the disease seems to affect them very little. We ignore it. Clean water plays a big part in helping them ward off this and other diseases.
Ich. In the winter, the chill on the way home (or other stresses) makes oscars (and other fishes) susceptible to ich parasites. Preventive treatment of their water with an ich cure really pays off. Half strength, please. Small oscars are really baby fish in spite of their comparatively large size.
Needs Space. Oscars not only need elbow room, they will take it from their tank mates (by killing or eating them). This applies to other oscars in limited quarters. You can uncomfortably house a single in a 20-gallon tank. They really need 30+ gallons. Two adults will co-exist in a 55. They need a 70. Four can live in the 70, but expect lots of arguments.
Like to Argue. Oscars also fight because they feel good, want to breed, or just want a little exercise. Their French web site calls them “toujour agressif.” Very aggressive describes oscars quite aptly.
Fighting or Spawning? Oscars fight by slapping each other while facing head to tail. They also lock lips and wrestle each other and try to bite chunks out of each other. (Typical pre-spawning behavior also.) Expect these arguments. If they get too violent, put in a divider. Add NovAqua to “bandage” their wounds and abrasions.
Good Fighters. Wild oscars in Florida escaped from flooded fish farm ponds or were released by fishermen who saw their fighting potential as a game fish. Their pugnacious natures make them a great fish to catch on hook and line. They put the “game” in game fish. They fight better than bass. They taste better, too.
Big Bruisers. Oscars break heater tubes, power filter intakes, under gravel filter stems, and floating thermometers. Some they break by running into them accidentally. Others they break on purpose. They consider these items “oscar toys.” If you replace them, your oscar will probably break them again. Use suction cup holders to reduce breakage and figure out less superfragilistic ways to replace broken equipment. If you want to give them a toy, toss in a ping pong ball occasionally.
Décor. Forget beautifully decorated planted aquaria like Amano-san constructs. Oscars rarely tolerate live plants. Use plastics. Weight the bottoms so they look normal when your oscars move them. (And they will.) Epoxy a gob of gravel on their base. Use the same gravel as their tank substrate. When they move them, the plants still look planted. Avoid rough rocks and sharp pieces of wood. Why ask for trouble? Arguing oscars can very easily injure themselves on sharp objects.
Growth Variation. If you start with equal-sized oscars, sometimes one grows faster. The big one gets most of the food and then grows even faster. Whip out your divider and separate them. Reduce the rations going into the large guy and give the extra to the little guy. He’ll catch up (usually). If you move one to a different tank, put the bigger guy in the smaller tank.
Preventing Stunting. You’ve heard many people say “fish grow to the size of their tank.” You can stunt an oscar in a 10-gallon tank. But why put one of these potentially huge fishes in a little tank? Get a neon tetra. Okay, so you had no idea how big he’d get and he’s in your 10-gallon tank. How do you keep from stunting him? Stunting results from the waste products in the water – not from bouncing off the glass walls. Just change the water more often and/or make larger changes. You can grow a huge (and very uncomfortable) oscar in a 10-gallon tank, if you change enough of his water often enough. So reach under your mattress and extract enough of your tax refund to house him right. Or get him a home equity loan.
Breeding Oscars. You won’t breed them in a 10. You need (minimum) a 55-gallon tank (70 gallons would be better). In fish farms they use a large diameter concrete pool two feet deep -- very similar to a kid’s wading pool in a public park, but with steep sides. They put in lots of large oscars and let them select their own mates. The breeder adds several large pieces of slate (some on the bottom, some leaning against the sides). The slates are checked frequently for spawns. Slates of eggs are removed and hatched artificially under controlled conditions. You can get bit walking thru these breeding ponds -- especially when extracting egg-filled slates.
Breeding Tank. In your breeding tank partially bury a large slab of slate. Let them dig it out themselves. (If they spawn on the filter plate, the eggs and fry get sucked under.) Take out the eggs. Do it at night, if you fear oscar hickies. You will have better results rearing the eggs artificially.
Oscar Eggs. Put the slate in a well-filtered 10-gallon tank and add a slow bubbling airstone as their surrogate mama. Add methylene blue to taste (circa 2 ppm). Most cichlid eggs are clear or a light amber color. Oscar eggs are a cloudy off-white nearly tan color. As they develop, a line divides the eggs in half. They hatch in three to seven days depending upon temperature.
Hatched Eggs. Oscar eggs hatch into an eyeless blob with a wiggling tail attached to the slate by an unseen thread. They look nothing like oscars (or fish). As they absorb their yolk sacs, they lose their sticky thread and fall to the bottom in a sticky clump. Most cichlids absorb their yolk sacs fairly quickly and turn into hungry baby fishes. Oscars take much longer and grow into much larger and hungrier fry. Once they grow eyes and fins, they will start swimming (and eating). They cannot eat until they become free swimming.
Oscar Fry. Very small oscars sport a black line down their sides (typical of predator fishes who tend their young in schools). If you’ve ever seen a male largemouth bass tending his pit of fry, you’ve seen the obvious relationship between our North American centrarchids and the South American cichlids. Oscar fry eat newly hatched brine shrimp – lots of it and often. You will not believe how much they can eat. You will need to change their water often.