Goldfish are popular freshwater fish that are often kept as pets. With their beautiful colors, flowing fins, and lively personalities, it’s no wonder they are so beloved. If you already have a goldfish, you may be wondering if you can add another one to keep it company.
If you don’t have time to read this full guide right now, here’s a quick answer: yes, you can keep two fancy goldfish together if you have at least 20 gallons of tank space per fish and adequate filtration. Fancy varieties should not be housed with single-tail common goldfish.
Basic Goldfish Care Requirements
Tank size
Goldfish require a large tank size to thrive. The general rule is to provide at least 20 gallons for the first goldfish, plus an additional 10 gallons per additional goldfish in the tank. This allows for adequate swimming space and dilutes waste products.
Fancy goldfish with rounded bodies require at least 30 gallons for the first fish. Goldfish produce a lot of waste, so a larger tank helps maintain water quality. We recommend a minimum tank size of 55 gallons when keeping multiple goldfish together.
Water parameters
Goldfish do best in cool water between 65-72°F. The pH should be maintained between 6.5-7.5. Ammonia and nitrite levels should always read zero, while nitrate should be kept below 20 ppm through regular partial water changes. Well-oxygenated water is also important.
Using an air pump and air stone helps improve oxygenation. Good water flow from the filter return also helps gas exchange at the surface.
Filtration
Goldfish are messy fish that produce a lot of waste, so robust filtration is a must. Canister filters provide excellent mechanical and biological filtration. Aim for a filter rated for at least twice the actual volume of the tank.
Adding extra filter media like ceramic rings, bio balls or filter floss also helps remove solid waste. Performing 25% partial water changes weekly helps remove dissolved organics.
Diet
Goldfish are omnivores and should be fed a varied diet. A high quality sinking pellet should make up the staple diet, supplemented with treats like blanched vegetables, live or frozen foods. Feed several small meals throughout the day rather than one large meal.
Only feed as much as the fish can consume within 2-3 minutes. Uneaten food should be removed to avoid fouling the water. Offer a mix of foods like:
- Sinking goldfish pellets
- Blanched vegetables like spinach, zucchini or peas
- Live or frozen brine shrimp, bloodworms or daphnia
- Sinking algae wafers
Avoid overfeeding and foods with lots of fillers. High protein diets can cause swim bladder issues in fancy goldfish. Offer treats sparingly to prevent obesity.
Can Two Fancy Goldfish Live Together?
Tank size recommendations
Fancy goldfish have unique care requirements when it comes to tank size. Although you can keep two fancy goldfish together, they need plenty of room to swim and grow. The general rule is 20 gallons for the first fancy goldfish, plus an additional 10 gallons per additional fancy goldfish.
So for two fancy goldfish, aim for at least a 30 gallon tank. Bigger is always better when it comes to goldfish tanks!
Some specific fancy goldfish types like orandas, black moors, and ranchus can grow quite large at 8-10 inches. Aim for an even bigger tank of 55+ gallons if keeping multiple fancy goldfish varieties known to get big.
More room allows goldfish to exhibit their natural behaviors and promotes healthy development.
Introducing new tankmates
When adding a second fancy goldfish to a tank, go slow with introductions. Start by floating the new goldfish’s bag in the tank for 15-20 minutes so the fish can acclimate to the temperature. Next, add a little tank water to the bag every 5 minutes for 30 minutes.
Finally, release the new goldfish into the tank.
Closely supervise both fish for signs of aggression, which is rare in fancy goldfish. But nipped fins, chasing, or one goldfish staying hidden indicate they may not get along. Try rearranging decor to break up line of sight before considering separating them.
Ongoing monitoring and care
Double check water parameters regularly when keeping two fancy goldfish together. Their higher bio load produces more ammonia, which is toxic. Test for ammonia, nitrite, and nitrate weekly and perform partial water changes as needed to keep levels low.
Feed both goldfish a varied, protein-rich diet 2-3 times daily. Signs of malnutrition like stunted growth or fading color indicate they need more food. Variety is key, so rotate between flakes, pellets, frozen foods like brine shrimp, and blanched veggies.
Lastly, keep a close eye on each goldfish’s health. Issues like swim bladder disease, which causes buoyancy problems, need prompt treatment. Catching illness early and separate sick fish helps stop disease spread between tankmates.
Should Single-Tail and Fancy Goldfish Be Housed Together?
When setting up a goldfish aquarium, a common question is whether different varieties of goldfish can live together peacefully. There are some important considerations when deciding whether to mix single-tail and fancy goldfish.
Differences between types
Single-tail goldfish like common and comet have long, single caudal fins. They tend to be slim-bodied and agile swimmers. Fancy varieties like orandas, fantails and ranchus have double tails, bulbous bodies, and other distinctive features like protruding eyes and wen growths.
These physical differences affect their swimming ability, metabolism, and oxygen needs. Single-tails are very active and need more swimming space. Fancies move slower and thrive in calmer tanks. Mixing the two can cause issues as the slimmer fish may outcompete fancier tankmates for food.
Reasons not to mix varieties
- Fancies produce more waste and need cleaner water than single-tail varieties.
- Aggressive eating by single-tails may starve slower fancy goldfish.
- Long single tails may nip at fancy goldfish and stress them.
- Rapid single-tails can exhaust slower moving fancy tankmates.
- Different goldfish breeds have different optimal temperature ranges for healthy digestion and growth.
Considering their different needs, housing single-tail comets with fancy fantails for example can compromise health and quality of life for one or both.
Alternatives to mixed tanks
Rather than mixing tail and body types in one tank, some better options are:
- Keep different varieties in separate species only tanks.
- Choose goldfish breeds with similar body shape and activity levels like comets and shubunkins.
- Select young fancy breeds which are more agile swimmers before features like wen and eyes develop.
Properly separating incompatible goldfish can prevent aggression, competition and health issues. It allows customizing their habitats and care for their unique needs. For example, faster moving single tails need bigger tanks, increased filtration and cooler water than delicate fancies.
While it’s tempting to mix goldfish for aesthetic variety, recovery is extremely stressful if conflicts arise. Strategic tankmates selection reduces disease transmission risk as well. Overall, the most ethical approach is keeping goldfish breeds with similar form and functions together for their wellbeing.
Sexing Goldfish and Breeding Concerns
Identifying male and female goldfish
Determining the sex of your goldfish can be tricky, but knowing whether you have males or females is important to avoid unplanned breeding. Male goldfish tend to be slimmer, smaller, and more active than females.
They also develop white spots called breeding tubercles on their gill covers and first pectoral fin during spawning season. Females have a rounder, thicker body shape and a protruding vent. Some other differences include:
| Males | Females |
| – More streamlined | – Rounder, heavier bodied |
| – Tubercles on gills and fins | – Protruding vent |
| – Few white spots less than 1mm | – Usually no tubercles |
Goldfish don’t exhibit obvious external sexual characteristics until they reach maturity. So in younger fish, it can be difficult to tell males and females apart. If unsure, isolating fish once they reach sexual maturity at around 12-18 months can help avoid accidental spawning.
Discouraging breeding behavior
If your tank houses both male and females, you’ll likely witness spawning behavior. The best way to discourage breeding is to avoid triggering factors that initiate courtship displays like warm temperatures, presence of plants/spawning sites, high quality foods, and water changes. Other tips include:
- Keep only same-sex groups
- Add tank dividers or extra plants/deco to disrupt mating cues
- Use cooler water temperatures around 65°-70°F to suppress spawning urge
- Limit protein-rich feeds that fuel breeding
- Avoid large or frequent partial water changes
You can minimize chances of breeding success by removing bubble nests, but odds still remain if the tank houses both males and gravid females. So prevention ahead of time is ideal to avoid dealing with hundreds of unplanned fry in your aquarium!
Caring for fry if eggs are laid
If your goldfish spawn successfully, you may soon have a tank teeming with eggs and then fry! A female goldfish can lay up to 1,000 eggs per season. Goldfish eggs hatch in 3-7 days at optimal 75°-80°F water.
Caring for goldfish fry requires a separate rearing or nursery tank with warm, clean water; gentle filtration; vegetation; infusoria culture food or special fry feeds. Daily partial water changes help maintain water quality as fry grow.
Within 6-8 weeks, they should reach 1⁄2 inch size and transition to crushed goldfish flakes. Most aquatic stores will adopt excess fry.
Raising baby goldfish is very rewarding but extremely time intensive. Alternately, products like Marina Hang on Breeding Boxes temporarily separate eggs/fry if unable to set up a separate tank. Simply move adults back to main tank once eggs hatch so fry can safely grow in the breeding box for 4-6 weeks before releasing.
Signs of Stress and Incompatibility
Aggression
Aggression is one of the most common signs that two goldfish are incompatible tankmates. This can manifest as chasing, nipping fins, or outright attacking each other. Male goldfish in particular can show aggression towards each other when competing for territory or food.
Females may also fight, especially if they are cramped in too small of a tank. If you notice one fish relentlessly chasing or nipping at the other, they likely need to be separated for their own safety and wellbeing.
Changes in Appearance or Behavior
Stressed goldfish may exhibit physical or behavioral changes. Look for clamped fins, loss of appetite, hiding, erratic swimming, or rubbing against objects. These are signs that the fish is anxious, uncomfortable, or unwell.
Potential causes include bullying from the other goldfish, poor water quality, or simply general incompatibility between the two fish. While some nipping or chasing can be normal as they establish a hierarchy, consistent stress is a red flag that they are not getting along.
Solutions for Rivalry Issues
If your goldfish are showing signs of aggression, stress, or incompatibility, there are a few potential solutions:
- Get a larger tank – More space reduces territory disputes. Aim for at least 20 gallons for two fancy goldfish.
- Add sight barriers – Plants, rocks, and decor can obstruct line of sight and provide hiding spots.
- Rearrange decor – Switching up their environment sometimes eases tension.
- Improve filtration – Overcrowding and poor water quality exacerbate problems.
- Try rescaping – Changing substrates, plants, etc. resets the territory.
- Separate permanently – Some goldfish just will not get along, necessitating separate tanks.
With patience and proper adjustments, rivalry issues between goldfish tankmates can often be resolved. However, if aggression persists despite your best efforts, permanent separation may be the only solution.
Observe your fish closely, and be prepared to act in their best interest if the relationship is simply not working out.
Conclusion
In summary, most fancy goldfish varieties can successfully be kept in pairs or small groups, provided adequate tank space and top-notch water quality are supplied. However, mixing tail types or allowing breeding are not recommended.
With some planning ahead and proper ongoing care, you can enjoy keeping two fun and lively goldfish pets.
