Fish
Fish are among the most colorful, peaceful, and fascinating creatures in the aquatic world. Having coexisted with humans for thousands of years, fish have become an essential part of the aquarium hobby. Discover the world's most comprehensive guide on fish adoption, fish care, fish species, fish prices, goldfish, betta fish, molly, guppy, tetra, aquarium setup, water quality, fish nutrition, fish health, fish diseases, fish breeding, how to tell fish age, how to tell fish gender, aquarium filters, and baby fish care on this page. With free fish adoption listings, fish for sale prices, fish breeding, and lost fish listings, petopic is here for you.
Fish Adoption
Fish adoption is one of the most meaningful ways to add a peaceful, colorful, and fascinating aquatic world to your life. Fish are quiet, easy to care for, and adaptable to home environments; however, they require proper aquarium conditions and regular maintenance. Therefore, the fish adoption process is not just about selecting a listing. You can acquire fish through free fish adoption, purchasing fish for sale, or fish breeding. Responsible fish ownership requires proper aquarium setup, water quality control, and regular maintenance.
Fish Adoption Process
The first step in the fish adoption process is determining the species that suits your lifestyle and experience level. For beginners, hardy species like goldfish, betta, molly, and guppy are recommended, while experienced hobbyists may prefer more delicate species. You can browse free fish adoption listings, research fish for sale prices, or acquire fry through fish breeding. Before adoption, you should evaluate aquarium size, filter system, water quality requirements, and nutrition costs.
Fish Adoption Requirements
Those wishing to adopt fish must have proper aquarium setup, equipment to monitor water quality, and time to dedicate to regular maintenance. Fish require regular water changes, filter maintenance, and proper nutrition. Aquarium size should be determined based on fish species and number. You can find the right fish for you by browsing free fish adoption listings on Petopic.
To browse free fish adoption listings and make an informed adoption:
Free Fish Adoption ListingsFish Prices
Fish prices vary significantly based on species, age, size, rarity, and health status. Goldfish prices, betta fish prices, molly prices, and tropical fish prices differ considerably from each other. While free fish adoption has zero cost, fry or rare species for sale can range from $5 to $5,000 and above. When researching prices, not only the purchase cost but also aquarium setup, filter system, heater, food, and annual maintenance expenses should be considered.
Goldfish Prices
Goldfish prices are among the most affordable ranges in the fish market due to this species' hardiness and popularity. Goldfish prices as of 2026 range from $2 to $50. Specially colored or rare varieties are priced higher. Free goldfish adoption listings are also available; you can browse these opportunities on our free fish adoption page. Since goldfish can live 10-15 years, long-term care costs must be planned.
Betta Fish and Small Species Prices
Betta fish prices, along with small tropical fish like guppy, molly, platy, and tetra, range from $3 to $50. Betta fish are popular due to their colorful appearance and ability to be kept alone. Specially colored or rare varieties are priced higher. Fish for sale prices from private sellers are generally more affordable; you can compare fish prices from sellers on our fish for sale listings.
Large and Rare Fish Prices
Discus, angelfish, cichlid, and rare tropical fish prices range from $20 to $500 and above. Discus fish are expensive due to rare color varieties and large sizes. Trained or special breeding individuals are sold at additional cost. For those searching for free fish, Petopic's free adoption category is a reliable option. After adoption or purchase, it's recommended to set aside an additional $100-1,000 budget for aquarium setup, filter system, heater, and first-year maintenance expenses.
2026 Popular Fish Species Price Comparison
Important Note: When adopting or purchasing fish, don't focus solely on price; also pay attention to the fish's health status, age, and aquarium conditions. Water quality testing, health check, and proper aquarium conditions should always be requested. Annual maintenance (food, filter materials, water changes) costs range from $50 to $300.
Fish Species
There are over 30,000 fish species in the world. More than 100 aquarium fish species are suitable for home care. From cold-water fish to tropical fish, from schooling fish to solitary fish, there's a fish species suitable for every lifestyle. When choosing a fish species, aquarium size, water temperature requirements, nutrition needs, and compatibility with other fish are of critical importance. You can find the right fish for you by filtering by species in free fish adoption and fish for sale listings.
Goldfish
Goldfish are one of the most popular and hardy species in the aquarium hobby. They are cold-water fish and can live 10-15 years. They come in different colors and varieties. Free goldfish adoption listings are frequently searched; however, this species requires large aquariums and regular water changes. Those wanting to learn about goldfish breeding signs, breeding season, and fry care can check our fish breeding page.
Betta Fish (Siamese Fighting Fish)
Betta fish are popular due to their colorful appearance and ability to be kept alone. They can be kept in small aquariums but may be aggressive with other betta fish. They are tropical water fish and require 22-28°C temperature. Betta fish adoption listings are common; if you've lost or found a fish, you can use our lost fish section.
Molly, Guppy, Platy, and Tetra
Livebearing fish like molly, guppy, platy, and tetra are popular due to their prolific nature and colorful appearance. They are schooling fish and should be kept in groups. They are tropical water fish and require 24-28°C temperature. Each has different nutrition, aquarium size, and water quality needs. On Petopic, you can filter free fish adoption, fish for sale, and breeding listings by species.
Free Fish Adoption
Free fish adoption is one of the most frequently researched options for those wanting to adopt fish. Free fish listings are usually opened for fish seeking new aquariums due to current conditions. Being free doesn't mean less care responsibility; fish require regular water changes, proper nutrition, and suitable aquarium conditions. You can acquire free fish from fish owners or adoption platforms. Free goldfish adoption searches are also common; this species is frequently rehomed due to its hardiness.
Free Fish Adoption Process
Free fish adoption process through Petopic: (1) Browse free adoption listings, (2) Fill out application form, (3) Meet with rehomer, (4) Learn about fish's aquarium conditions and evaluate compatibility, (5) Check aquarium and water quality, (6) Sign contract and receive fish. Fish health check is recommended after adoption. In free fish listings from owners, the fish's health status, feeding habits, and reason for rehoming must be learned.
To see free fish adoption listings:
Free Fish Adoption ListingsFish for Sale
Fish for sale listings include fry or adult, rare or common fish species. Fish sale prices vary by species, age, and characteristics. When purchasing fish for sale, request water quality testing, health check, and proper aquarium conditions. Petopic is a platform that connects sellers with buyers; we don't sell animals, we provide listing services.
Fish for Sale Listings and Prices
Small species (guppy, tetra, molly) range from $2-20, medium-sized species (betta, platy, angelfish) from $5-50, large species (discus, cichlid, rare tropical fish) from $20-500+ USD. Fry are generally 20-30% more expensive than adults. Specially colored or rare varieties are sold at additional cost. You can search using species, age, price, and location filters in our fish for sale listings.
To browse fish for sale listings:
Fish for Sale ListingsFish Breeding
Fish breeding requires suitable mate selection, health checks, and proper water conditions for healthy fry. Questions like molly breeding signs, guppy breeding season, and betta fish breeding are frequently researched. Before breeding, it's recommended that both fish undergo health checks and water quality tests. On Petopic, fish breeding listings connect owners seeking mates or offering their fish for breeding.
Fish Breeding Age and Conditions
Female fish are generally suitable for first breeding between 6-12 months; males can start between 4-8 months. Large species are bred at a later age. Suitable water temperature, pH value, and aquarium setup should be provided for breeding. Breeding agreements should include party information, fish information, financial terms, and fry rights. You can browse listings from our fish breeding page.
To see breeding partner listings:
Fish Breeding ListingsLost Fish
If you've lost your fish or found a missing fish, you can create a listing on Petopic. Lost fish listings, lost aquarium fish listings, and lost fish searches are frequently made. Fish can jump out of aquariums, enter filter compartments, or hide behind decorations; opening an early listing increases the chance of being found. Rather than lost fish price or lost fish prices, the main focus should be the fish safely returning to the aquarium. Those who found fish can match with listings and reach owners.
How to Find a Lost Fish?
Lost fish are usually found inside the aquarium in filter compartments, behind decorations, plant roots, or outside the aquarium in nearby areas (moist surfaces, puddles). Detailed search inside the aquarium, filter and decoration checks should be done. For fish lost outside the aquarium, moist areas, puddles, and nearby surroundings should be checked. Informing others, spreading listings, and using our lost fish platform is critical. Found fish may be tired, stressed, or injured, so they should be kept in a calm environment and quarantined under proper water conditions. Listings should detail the fish's species, color, size, location where it was lost, and special markings.
To create a lost fish listing or view listings:
Lost Fish ListingsAquarium Setup
Aquarium setup is the foundation of fish ownership. Proper aquarium size, filter system, heater, lighting, and decoration are critical for fish health. Aquarium setup should be planned according to fish species and number. Small aquariums (20-50 liters) are recommended for beginners, while experienced hobbyists may prefer large aquariums (100+ liters).
Aquarium Size Selection
Aquarium size should be determined based on fish species and number. General rule: 1 liter of water per 1 cm of fish is calculated. However, this is a minimum value; larger aquariums are always better. Minimum 50 liters for goldfish, minimum 20 liters for betta fish, minimum 60 liters for schooling fish are recommended. Larger aquariums maintain water quality better and reduce fish stress.
Filter System
Filter system is essential for keeping aquarium water clean and healthy. There are options like internal filter, external filter, and sump filter. Filter capacity should be 3-5 times the aquarium volume. Filter media (biological, mechanical, chemical) should be cleaned and replaced regularly. In new aquariums, the filter system's cycling process can take 2-6 weeks.
Heater and Lighting
Heater is essential for tropical fish. Heater power is determined based on aquarium volume (general rule: 1 watt per 1 liter). Water temperature should be maintained between 22-28°C. Lighting is important for planted aquariums. LED lighting is energy-efficient and long-lasting. Daily 8-12 hours of lighting is sufficient.
Water Quality & Parameters
Water quality is the most critical factor for fish health. pH, ammonia, nitrite, nitrate, water hardness, and temperature should be checked regularly. Water quality problems are the most common cause of fish diseases and deaths. Regular water changes, filter maintenance, and water quality testing are essential for a healthy aquarium.
pH Value
pH value indicates the acidity-alkalinity level of water. Ideal pH for most aquarium fish is between 6.5-8.0. 7.0-7.5 for goldfish, 6.5-7.5 for tropical fish are recommended. pH value should be tested weekly, and sudden changes should be avoided. Special products can be used to lower or raise pH, but it should be done gradually.
Ammonia, Nitrite, and Nitrate
Ammonia and nitrite are toxic to fish and should be zero. Nitrate can be tolerated at low levels (below 20 ppm). In aquariums where the nitrogen cycle (cycling) is not completed, ammonia and nitrite rise. Regular water changes (20-30% weekly) and filter maintenance keep these values under control. Water quality should be checked weekly with a test kit.
Water Changes
Water changes are the most important part of aquarium maintenance. Weekly 20-30% water changes are recommended. During water changes, chlorine and heavy metals should be removed, and water temperature should match aquarium water. Fish should not be stressed during water changes, and sudden temperature changes should be avoided.
Fish Nutrition
Fish nutrition should be done with species-appropriate quality food, regular meals, and correct amounts. Overfeeding deteriorates water quality and negatively affects fish health. Each fish species has different nutrition needs; they can be carnivorous, herbivorous, or omnivorous. Daily 1-2 meals, an amount that can be consumed in 2-3 minutes, should be fed.
Fish Food Types
There are options like flake food, pellet food, tablet food, frozen food, and live food. Flake food is for small fish, pellet food is for medium-large fish. Tablet food is for bottom fish, frozen food (artemia, bloodworms) is used for protein supplementation. Live food provides natural nutrition for fish but carries disease risk. When choosing food, species-appropriate formulations should be preferred.
Feeding Schedule
Daily 1-2 meals are sufficient. Food should be fed at regular times, morning and evening. Food amount should be enough to be consumed in 2-3 minutes. Excess food deteriorates water quality and negatively affects fish health. Fasting days (1-2 days per week) are beneficial for fish health. Fry should be fed more frequently (3-4 meals daily).
Fish Health & Diseases
Fish health is maintained through regular observation, water quality control, and early disease detection. Fish diseases can be caused by parasites, bacteria, fungi, and water quality problems. When disease symptoms are seen, quarantine and treatment should be applied immediately. Prevention is more important than treatment; regular maintenance and water quality control prevent diseases.
Common Fish Diseases
White spot (Ich), fungal infection, fin rot, dropsy, pop-eye, and parasite infections are common. White spot appears as small white dots and is treated with temperature increase. Fungal infection appears as cotton-like white growths and is treated with antifungal medications. Fin rot appears as fin deterioration and redness and is treated with antibiotics. When disease symptoms are seen, the sick fish should be quarantined and appropriate treatment applied.
Disease Prevention
Regular water changes, filter maintenance, water quality control, and quarantine are the foundation of disease prevention. New fish should be kept in quarantine for 2-4 weeks before being added to the aquarium. Care should be taken when using live food, and frozen food should be preferred. Stress factors (sudden temperature changes, overcrowding, aggressive fish) should be reduced.
Fish Breeding & Fry Care
Fish breeding varies by species. Livebearing fish (guppy, molly, platy) give birth to fry, while egg-laying fish (goldfish, betta, tetra) lay eggs. Proper water conditions, nutrition, and mate selection are important for breeding. Fry care varies by species; some species protect their fry while others may eat them.
Livebearing Fish
Livebearing fish like guppy, molly, platy, and guppy give birth to fry. Female fish show pregnancy signs (abdominal swelling, dark gravid spot). After fry are born, they should be kept separate from adult fish. Fry should be fed with special fry food or crushed flake food. Fry aquarium requires clean water and regular feeding.
Egg-Laying Fish
Egg-laying fish like goldfish, betta, tetra, and cichlid lay eggs. Suitable water conditions, temperature increase, and mate selection should be provided for spawning. Eggs should be kept separate from adult fish or egg protectors should be used. Eggs hatch within 2-7 days, and fry should be fed with special food.
How to Tell Fish Age & Gender?
Questions about how to tell fish age and how to tell fish gender are frequently asked during the fish adoption or purchase process. While age and gender determination is easy in some species, experienced observation or veterinarian examination may be required in others. Age determination is important for understanding the fish's health status and nutrition needs. Gender determination is necessary for breeding plans.
How to Tell Fish Age?
Size: Fry are small, adults are larger. However, size varies by species and nutrition. Fins: In fry, fins are smaller and softer; in adults, they are larger and harder. Color: Colors may be paler in fry, more vibrant and bright in adults. Behavior: Fry may be more active and curious, older fish may be calmer. Fish records or veterinarian examination are needed for definitive age determination.
How to Tell Fish Gender?
Visual differences: In some species (betta, guppy, molly), male and female colors and fin shapes differ. Male betta fish have longer fins and are more colorful; females have shorter fins and are paler. In guppy, males are more colorful and smaller; females are larger and paler. Behavior: Males are generally more aggressive and showy; females may be calmer. However, these generalizations are not always valid. Veterinarian examination: Definitive gender determination may require veterinarian examination in some species. Gender determination is essential if you're planning fish breeding.
Aquarium Maintenance
Aquarium maintenance includes regular water changes, filter cleaning, glass cleaning, and decoration maintenance. Regular maintenance is critical for fish health and water quality. A weekly maintenance routine should be established and applied consistently.
Weekly Maintenance Routine
Weekly maintenance: 20-30% water change, filter media check, glass cleaning, food residue cleaning, and water quality testing should be done. Monthly maintenance: Filter media replacement, decoration cleaning, plant care, and general aquarium check should be done. Annual maintenance: Major cleaning, equipment check, and aquarium renewal if necessary should be done.
Filter Maintenance
Filter media should be rinsed with clean water 2-3 times the aquarium volume. Tap water should not be used; chlorine and chemicals can kill biological filter. Filter media replacement should be done gradually, and biological filter should be preserved. Filter pump and hoses should be checked regularly and cleaned if clogged.
Frequently Asked Questions
How does the free fish adoption process work?
Free fish adoption process: (1) Browse free adoption listings, (2) Fill out application form, (3) Meet with rehomer, (4) Learn about fish's aquarium conditions, (5) Check aquarium and water quality, (6) Sign contract and receive fish. Fish health check is recommended after adoption.
What are fish prices?
Small species (guppy, tetra) range from $2-20, medium-sized species (betta, molly) from $5-50, large species (discus, cichlid) from $20-500+ USD. Prices vary by fish species, age, rarity, and health status. You can check current prices from our fish for sale listings.
Which fish species are suitable for beginners?
Fish species suitable for beginners: Goldfish (hardy, cold water), Betta fish (can be kept alone), Guppy (schooling fish, prolific), Molly (social, hardy), and Tetra (schooling fish, colorful). These species are easy to care for and hardy.
How often should aquarium water be changed?
Weekly 20-30% water changes are recommended. More frequent changes can be done in small aquariums (20-50 liters), less frequent in large aquariums (100+ liters). Water quality testing should check ammonia, nitrite, and nitrate levels, and water change frequency should be increased if necessary.
How to prevent fish diseases?
Regular water changes, filter maintenance, water quality control, and quarantine are the foundation of disease prevention. New fish should be kept in quarantine for 2-4 weeks before being added to the aquarium. Stress factors (sudden temperature changes, overcrowding) should be reduced. Quarantine and treatment should be applied immediately when disease symptoms are seen.
What age is appropriate for fish breeding?
Female fish are generally suitable for first breeding between 6-12 months; males can start between 4-8 months. Large species are bred at a later age. Proper water conditions, nutrition, and mate selection are important for breeding. You can browse listings from our fish breeding page.
How to find a lost fish?
Lost fish are usually found inside the aquarium in filter compartments, behind decorations, or outside the aquarium in nearby areas. Detailed search, filter check, and creating lost fish listings is critical. Found fish should be quarantined under proper water conditions.
How is aquarium size determined?
General rule: 1 liter of water per 1 cm of fish is calculated. However, this is a minimum value; larger aquariums are always better. Minimum 50 liters for goldfish, minimum 20 liters for betta fish, minimum 60 liters for schooling fish are recommended. Larger aquariums maintain water quality better.
How to tell fish age?
Size, fin shape, color, and behavior provide clues for age determination. Fry are small and pale; adults are larger and more colorful. Fish records or veterinarian examination are needed for definitive age determination.
How to tell fish gender?
In some species (betta, guppy, molly), male and female colors and fin shapes differ. Male betta fish have longer fins and are more colorful; females have shorter fins and are paler. Veterinarian examination may be required for definitive gender determination in some species.
Find Your Fish with Petopic
World's most comprehensive fish platform: free fish adoption, fish for sale, fish breeding, and lost fish. We're here with all information about aquarium setup, water quality, nutrition, health, and breeding.