Full Grown Fantail Goldfish: Size, Lifespan, Price & More

This care guide covers everything you need to know about caring for a fantail goldfish once it has reached its full adult size. We'll cover their normal size, weight, appearance, personality, feeding needs, health concerns, and more to help you keep your fully grown fantail fish happy and healthy for years to come.

Size at Full Grown

Fantail goldfish can reach sizes of 8-10 inches long from nose to tailfin when fully mature. Females tend to grow slightly larger than males on average.

Their dorsal and ventral fins will also be fully expanded at adulthood.

While they may still grow very slowly once fully grown, they have generally achieved their maximum potential size after 2-3 years.

Weight at Full Grown

A large, fully grown fantail goldfish can weigh up to 1 pound. Most will be in the 8-12 ounce range. Proper nutrition is important for achieving their genetic size potential.

Overfeeding can lead to weight issues, while underfeeding can stunt their growth. Aim to only feed them what they can consume in a few minutes each day.

Appearance at Full Grown

At maturity, a fantail goldfish's appearance is quite distinctive. Their bodies will be streamlined and torpedo-shaped. The dorsal and ventral fins will be elongated and fantail-shaped, giving them their name. Fins will be colored to match the gold, orange, white or calico coloring of their scales. Eyes may be bulging due to genetics. Their skin should be smooth and scales tight-fitting without any lesions or fins becoming ragged.

Personality at Full Grown

Fantail goldfish tend to be quite docile even as adults. They can become more territorial of their tank space, so it's best to house just one large fish alone rather than risk aggression issues.

Once accustomed to your presence, they may even come to the glass to greet you during feedings. Despite their placid nature, plenty of stimulation like live plants helps prevent boredom.

Price

High quality, fully grown fantail goldfish can sell for $15-30 each depending on their unique coloring and finnage.

Fancy varieties with extra-long fins may command higher prices. It's best to shop from reputable breeders that health-test their stock to avoid potential diseases.

Food/Feeding

At their adult size, fully grown fantails still need a nutritious diet but in smaller quantities.

Aim to feed 1-2 teaspoons of good quality aquarium fish food per day, spread into 2-3 meals. Food should be less than the space between their eyes to prevent bloating.

Variety is best - try small frozen bloodworms or brine shrimp a few times a week as a treat. Uneaten food should be removed to maintain water quality.

Lifespan

When kept in optimum conditions, fantail goldfish can live 5-10+ years as adults.

Proper water parameters, occasional water changes, suitable tank mates if any, and a varied diet supports their long natural lifespan.

Older fish may show signs of aging like slowing down, loss of color or appetite changes.

Health at Full Grown

Maintaining excellent water quality is essential for health as an adult. Monitor parameters closely and change 25-50% of the water weekly in a suitably sized aquarium (minimum 29 gallons for one large fish).

Watch for signs of common diseases like fin rot, body slime, popping eye or dropsy.

A balanced diet prevents nutritional deficiencies.

Provide hiding spaces to reduce stress.

An annual fish health check and necessary treatments protects them long-term.

Care and Nutritional Needs at Full Grown

Some key care aspects once fully grown include:

• Tank filtration rated for 3x the tank size
• Water changes every 4-7 days for optimal water quality
• Temperature between 68-78°F
• Low water flow from filters to avoid stress
• Hiding places like terracotta pots or Java Fern for resting/hiding
• Varied diet including quality pellets/flakes, plus occasional treats
• Décor for stimulation and shade like floating plants
• Monitoring for signs of stress, illness or injury

Costing

Long-term care costs once an adult include:

• Fish food: $5-10 per month depending on brand
• Water conditioner: $10-15 per 6 months bottle
• Filter media replacement: $10-20 every 6-12 months
• Full aquarium setup: $150-300 for a minimum 30 gallon tank
• Annual vet checkup: $30-50 depending on location
• Potential medications: $10-30 if illness occurs

Possible Behavioural Changes of a Fully Grown

As fantails mature into adulthood, some behavior shifts may be observed compared to their juvenile stages:

• Increased confidence and boldness around tank inhabitants and owners
• Less active swimming and more resting periods due to size
• More territorial over tank space and decor if housed alone
• May establish feeding response to owners at regular times
• Potentially less social if kept in same-sex groups of adults

Notable Characteristics of a Fully Grown

Some defining traits to look for in a healthy, fully grown fantail goldfish include:

• Streamlined torpedo body 8-10 inches long
• Large bilateral dorsal and ventral tails flowing behind body
• Bold, bright colors of orange, yellow, white or calico patterns
• Bulging eyes not sunk in or cloudy looking
• Smooth scales with no lesions, fin damage or body slime coat issues
• Responsive, calm temperament when approached or fed
• Regular, enthusiastic feeding responses at meal times
• Grazes aquatic plants, decor, tank sides if appropriately sized home
• Healthy pooping behavior without symptoms of maladies

Summary

With the proper care outlined here, fantail goldfish can live fulfilling lives into adulthood and beyond. Their unique and elegant fins paired with calm dispositions make them a favorite aquarium pet for many. Following best practices for nutrition, housing conditions and preventive healthcare ensures these beautiful fish thrive into old age. With some extra effort, fantails reward keepers with many years of enjoyment.