Full Grown Oscar Fish: Size, Appearance, Price & More

The Oscar fish is a popular freshwater aquarium fish known for its striking coloration and large size. In this guide, we'll cover everything you need to know about oscars when they reach their full grown size including their appearance, personality, care requirements, and more.

Size at Full Grown

Oscars can grow quite large, reaching 8-12 inches as adults. Females generally top out around 8-10 inches while males may attain lengths of 10-12 inches. Their body will also become thick and robust.

It's important to realize just how big oscars get so you can house them properly in a large aquarium as juveniles.

Weight at Full Grown

Corresponding to their size, fully grown oscars are heavy fish. Males typically weigh 1-2 pounds while females average 0.75-1.5 pounds. The largest oscars on record have tipped the scales at over 3 pounds.

I will say you should provide strong filtration and current in your tank to support such a large, active fish.

Appearance at Full Grown

As oscars mature, their coloration intensifies and contrasts more distinctly. Males in particular demonstrate brighter oranges, yellows, and blacks.

Females stay more muted grey/green overall.

Both sexes develop dark vertical bars running the length of their bodies. Their eyes also become more pronounced and intense. The oscar's torpedo-shaped body remains streamlined at maturity.

Personality at Full Grown

Adult oscars tend to be more confident and bold compared to juveniles. Their large size commands respect from tankmates. However, they also become more territorial over their personal space.

It's best to house them singly in the home aquarium unless you have an extremely large tank.

Be prepared for oscars to be the dominant "boss" fish in the system at full size.

Price

Mature oscars command a higher price tag versus juveniles due to their large size. Expect to pay $15-30 each for established adults, depending on availability from your local fish store or an online seller.

High-quality, show-worthy specimens may cost up to $50-75 each. The bigger the oscar, the greater the investment needed.

Food/Feeding

The dietary needs of full grown oscars are substantial.

Offer them a varied selection of foods at least twice per day such as sinking wafers/pellets, frozen bloodworms, brine shrimp, mysis shrimp, tilapia, and small feeder fish.

Their pellets should be at least 1/2 inch in size for adult oscars.

Increase feedings for breeding pairs or those kept singularly. Remove any uneaten food to maintain water quality.

Lifespan

With excellent care, oscars have the potential to live 10-15 years on average as adults. Top-quality maintenance in an appropriately sized aquarium is critical to supporting their long lifespan.

Water changes, balanced nutrition, and low stress are key to keeping adult oscars healthy for many years to come.

Health at Full Grown

Some health issues can emerge with aging oscars such as tumors, bacterial/fungal infections, and organ damage from poor water conditions over time.

You should monitor parameters closely and watch for behavioral changes, loss of appetite, bloating/lesions on the fish as signs of disease.

And again, having a veterinarian experienced in treating large cichlids available is advisable for mature oscars.

Care and Nutritional Needs at Full Grown

• House adults singly or in pairs in at least a 55-75 gallon tank or larger depending on size
• Maintain water temperature around 78-82°F
• Test and change 20-30% of tank water weekly for big fish waste production
• Use a strong external canister filter rated for your tank size
• Add aquarium salt for improved immune function at 0.25 tsp per 5 gallons
• Offer Nutritionally balanced foods suited for large cichlids in multiple feedings daily
• Monitor water parameters closely and perform partial water changes if ammonia or nitrites rise
• Test water quality monthly and deep clean tank hardware in established setups

Costing

Housing and caring for full grown oscars requires substantial resources. Allow a minimum budget of $300-500 to setup a suitable aquarium, purchase the fish, buy equipment, and stock consumables for nutritious adult oscar care.

Factor in additional water change supplies, media replacements, heater replacements, and any incidental veterinary costs over time as well.

Possible Behavioral Changes of a Fully Grown

Some oscars develop more aggressive or territorial tendencies as adults compared to younger specimens. Ensure adequate swimming space, hiding places, and sight-blocking decor to help diffuse conflict.

Pairs or groups established early often remain stable. Single specimens may spar or nip at additions.

Monitor interactions closely and be ready to separate combatants with a divider if needed.

Notable Characteristics of a Fully Grown

• Large, torpedo-shaped body up to 1 foot long in males
• Dark vertical barring along the sides
• Prominent eyes positioned high on the head
• Powder blue, orange, black, and yellow coloration highly developed
• Thick-bodied with a rounded anal fin
• Confident and bold demeanor, highly active
• Omnivorous diet needed for proper nutrition
• Hardy temperature and pH tolerance as adults
• Lifespan up to 15+ years possible with optimum care