Goldfish are popular freshwater fish that can make fun, interactive pets. Their vibrant colors and playful personalities have captivated aquarists for centuries. If you’re considering getting goldfish for the first time, tank size is an important factor to research beforehand.
Specifically, many prospective goldfish owners ponder: how many goldfish can live comfortably in a small, 5 gallon tank?
If you’re short on time, here’s a quick answer to your question: Ideally, a 5 gallon tank should house just one fancy goldfish, with no other tankmates. This allows ample room for swimming and offers adequate water volume to dilute waste. But what if you want more than one goldfish?
Read on as we dive deeper into ideal goldfish tank capacity.
In this roughly 3000 word article, we’ll cover key considerations regarding housing multiple goldfish in a 5 gallon aquarium. Topics include goldfish biology, behavior, waste output, tankmate compatibility, aquarium cycling, filtration, water changes, and more.
You’ll also find specific stocking recommendations for fancy goldfish breeds. Let’s explore how to healthily keep goldfish based on years of fishkeeper wisdom and scientific study.
Basic Goldfish Care Needs
Goldfish Anatomy and Life Expectancy
Goldfish have a unique anatomy that allows them to thrive in aquarium environments. They have a single dorsal fin on their backs and a pair of pectoral fins near their gills. Goldfish don’t have stomachs, so they need to graze on food consistently throughout the day.
Common goldfish typically live for 10-15 years with proper care and conditions.
Waste Production and Oxygen Needs
Goldfish are messy fish that produce a lot of waste. Their digestive systems are not very efficient, so they expel a lot of ammonia. This ammonia builds up quickly and contaminates the water if not filtered properly.
Goldfish require strong filtration and frequent partial water changes to maintain safe water parameters. They also need robust aeration and oxygenation since their waste consumes oxygen.
Swimming and Activity Requirements
Goldfish are active swimmers that need adequate space to thrive. Common goldfish can grow over 12 inches long and require at least 20 gallons for the first fish and 10 gallons for each additional fish. Fancy goldfish are smaller but still produce lots of waste.
They need at least 10 gallons for the first fish and 5 gallons for each friend. The tank should be wide, not tall, to provide ample surface area for swimming and gas exchange. Goldfish also appreciate smooth gravel or sand substrate for resting and digging.
Stocking Considerations for a 5 Gallon Goldfish Tank
Juvenile vs Adult Goldfish
When stocking a small 5 gallon tank, it’s crucial to consider the size of the goldfish. Adult fancy goldfish can grow over 6 inches long and require much more space than a 5 gallon can provide. However, juvenile fancy goldfish under 2 inches could temporarily housed in a 5 gallon.
Key factors are water quality and growth rate.
Goldfish produce a heavy bioload that requires strong filtration and frequent water changes. In a 5 gallon tank, ammonia and nitrites quickly accumulate to toxic levels. While juveniles produce less waste for the first few months, their rapid growth still demands diligent tank maintenance.
Ideally, juvenile fancies should be upgraded to a larger tank within 6 months. At 2-3 inches long, stunted growth, disease outbreaks, and early mortality become imminent in cramped living conditions due to their large bioload.
Single Fish vs Multiple Tankmates
While a 5 gallon tank can house small juveniles, it can only accommodate one fancy goldfish at a mature size. Despite their small stature, fancy varieties have hefty appetites and make lots of waste.
Adding tankmates further escalates water quality issues. With their intensive care needs, goldfish should really be kept species-only. Fancies also lack speed to compete with lively tankmates at feeding time. Ultimately, its best to keep a single fancy goldfish in a 5 gallon tank.
Fancy Breed Recommendations
When selecting a goldfish for a 5 gallon tank, fancy breeds with a maximum length around 4 inches are the only suitable options. Excellent choices include:
- Pearlscale
- Celestial Eye
- Pompom
These breeds remain relatively small, yet have the cute characteristics fancys are prized for. Avoid Comets, Commons, Shubunkins, Orandas, Fantails, and other large growing breeds exceeding 6 inches that require much larger aquariums.
| Breed | Max. Size | Recommended Minimum Tank Size |
|---|---|---|
| Pearlscale | 3-4 inches | 5 gallons |
| Celestial Eye | 4 inches | 5 gallons |
| Pompom | 3-4 inches | 5 gallons |
When selecting tankmates, avoid other fish species which may nip fins or outcompete for food. Keep only one small fancy goldfish in a 5 gallon tank to avoid health issues.
For more goldfish care tips, check out comprehensive goldfish care guides on The Spruce Pets.
Equipment Considerations for Goldfish Tanks
Filters
Goldfish are messy fish that produce a lot of waste, so powerful filtration is essential for keeping water quality high. The general recommendation is to have a filter capable of turning over the full volume of the tank at least 4-5 times per hour.
For a 5 gallon tank, you’ll want a filter with a flow rate of at least 20-25 gallons per hour (gph). The best options are canister filters or hang-on-back (HOB) filters designed specifically for goldfish.
Heaters
Fancy goldfish do best in water temperatures between 65-72°F while common goldfish prefer even cooler temps of 60-72°F. A 5 gallon tank is small enough that room temperature may be sufficient to keep the water in the ideal range.
If needed, a low wattage heater around 25-50 watts can be added, but make sure to monitor the temperature regularly.
Lighting
Moderate lighting between 5-10 hours per day is recommended. Goldfish do not require special aquarium lighting, so a simple fluorescent or LED hood light is all that is necessary. Avoid intense lighting as too much light can cause stress and encourage algae growth.
Decorations and Substrate
Be selective when choosing decorations and substrate for a goldfish tank. Sharp decor or small gravel can be harmful if accidentally ingested. Smooth, river-type stones and larger gravel size around 5-10mm is safest. Also avoid decor with small openings where goldfish can become trapped.
Live plants can help with water quality but must be able to withstand goldfish grazing. Some good options are anubias, java fern, and cryptocorynes.
Water Management Guidelines
Nitrogen Cycling
Nitrogen cycling is an essential biological process that removes harmful ammonia and nitrites from the aquarium water. It involves beneficial bacteria that convert fish waste and uneaten food into less toxic nitrate.
In a new 5 gallon goldfish tank, cycling the tank properly can take 3-8 weeks before adding fish to avoid exposure to unsafe ammonia and nitrite levels. Using a liquid bacterial additive like Tetra SafeStart Plus can help speed up nitrogen cycling by quickly establishing the nitrifying bacteria colony.
Partial Water Changes
Frequent partial water changes are crucial for limiting the accumulation of nitrates and replacing depleted minerals in a densely stocked small goldfish tank. For a 5 gallon aquarium, aim to replace 15-30% of the water at least twice per week.
Use a gravel vacuum to remove solid waste during water changes. Use water conditioner to remove chlorine and heavy metals whenever adding new water. More frequent or larger water renewals may be needed depending on factors like overfeeding, overstocking, and filtration capacity.
Testing Kits
Using reliable testing kits for ammonia, nitrites, nitrates, pH, and hardness allows close monitoring of water quality between changes. For 5 gallon goldfish tanks, aim for 0 ppm ammonia and nitrites, < 10 ppm nitrates, pH between 7.0-8.0, temperature between 65°-75°F.
Making adjustments based on regular test results helps maintain optimal water conditions and prevent dangerous spikes that could make goldfish sick. Some recommended testing kits include the API Freshwater Master Test Kit and the Tetra EasyStrips 6-in-1 test strips.
By following these key guidelines for nitrogen cycling, frequent partial water renewals, and regular testing, even small 5 gallon goldfish aquariums can maintain the clean, healthy water goldfish need to thrive.
Conclusion
While goldfish are commonly thought of as low-maintenance starter fish, their care needs are quite complex for long, healthy lives. By understanding goldfish biology and thoroughly planning a 5 gallon setup, just one fancy goldfish can thrive with diligent tank maintenance.
For multiple goldfish, bigger is always better regarding tank size and robust filtration. We hope this outline helps you make an informed decision if a 5 gallon tank suits your goldfish plans. Let us know if you have any other goldfish care questions!
