One of the biggest mistakes new goldfish owners make is choosing a tank that’s too small. Many people still believe goldfish can live happily in bowls or tiny aquariums, but the reality is very different.
Goldfish are active fish that produce a large amount of waste. They need plenty of swimming space and stable water conditions to stay healthy. A properly sized aquarium not only helps your fish grow but also makes maintenance much easier.
If you’re still planning your aquarium, start with our How to Set Up a Goldfish Tank guide before choosing a tank size.
Why Tank Size Matters for Goldfish
Unlike many tropical fish, goldfish constantly produce waste.
A small aquarium can quickly develop:
- Ammonia spikes
- Poor water quality
- Low oxygen levels
- Stunted growth
- Increased disease risk
A larger tank provides more water volume, making it easier to maintain stable conditions.
Think of tank size as one of the most important parts of goldfish care.
Goldfish Tank Size Chart
| Goldfish Type | Minimum Tank Size |
| Fantail Goldfish | 20 gallons |
| Oranda Goldfish | 20 gallons |
| Ranchu Goldfish | 20 gallons |
| Black Moor Goldfish | 20 gallons |
| Telescope Goldfish | 20 gallons |
| Lionhead Goldfish | 20 gallons |
| Bubble Eye Goldfish | 20 gallons |
| Common Goldfish | 55 gallons |
| Comet Goldfish | 75 gallons |
| Shubunkin Goldfish | 75 gallons |
For every additional fancy goldfish, add approximately 10–20 gallons.
Fancy Goldfish Tank Size Requirements
Fancy goldfish include:
- Oranda
- Ranchu
- Fantail
- Black Moor
- Telescope
- Lionhead
- Bubble Eye
These varieties have shorter, rounder bodies and are slower swimmers than single-tail goldfish.
One Fancy Goldfish
A 20-gallon aquarium is the minimum recommended size.
This provides enough room for swimming while maintaining stable water conditions.
Two Fancy Goldfish
A 40-gallon aquarium works well for most pairs.
The additional water volume helps manage waste production.
Three Fancy Goldfish
A 55-gallon aquarium is usually a good starting point.
Many experienced keepers prefer even larger tanks for long-term success.
If you’re interested in keeping fancy varieties, our Fancy Goldfish Care Guide covers their unique needs in detail.
Common Goldfish Tank Size Requirements
Common Goldfish are often sold as small fish, but they can eventually reach over 12 inches in length.
Unlike fancy goldfish, they are powerful swimmers that require significantly more space.
One Common Goldfish
A minimum of 55 gallons is recommended.
Two Common Goldfish
A 75 to 90-gallon aquarium is a better choice.
Multiple Common Goldfish
At this point, many owners move to stock tanks or outdoor ponds.
For indoor aquariums, larger is always better.
Shubunkin Tank Size Requirements
Shubunkins are single-tail goldfish that grow much larger than most beginners expect.
Because of their active nature, they need plenty of swimming room.
One Shubunkin
At least 75 gallons.
Two Shubunkins
100 gallons or larger.
Many Shubunkins eventually thrive better in ponds than aquariums.
Learn more in our Shubunkin Goldfish Care Guide.
Oranda Goldfish Tank Size
Orandas are among the most popular fancy goldfish.
Although they grow more slowly than Common Goldfish, adults can still reach 8 to 10 inches.
Recommended tank sizes:
| Number of Orandas | Tank Size |
| 1 | 20–30 gallons |
| 2 | 40 gallons |
| 3 | 55 gallons |
For more information, see our Oranda Goldfish Care Guide.
Ranchu Goldfish Tank Size
Ranchus are compact but still require substantial swimming space.
Recommended setup:
| Number of Ranchus | Tank Size |
| 1 | 20 gallons |
| 2 | 40 gallons |
| 3 | 55 gallons |
Read our Ranchu Goldfish Care Guide for breed-specific care tips.
Black Moor Tank Size
Black Moors have delicate protruding eyes and benefit from spacious aquariums with smooth decorations.
Recommended sizes:
| Number of Black Moors | Tank Size |
| 1 | 20 gallons |
| 2 | 40 gallons |
| 3 | 55 gallons |
Learn more in our Black Moor Goldfish Care Guide.
Telescope Goldfish Tank Size
Telescope Goldfish require similar space to other fancy varieties.
Because of their poor eyesight, overcrowding should be avoided.
Recommended sizes:
- 20 gallons for one fish
- 40 gallons for two fish
- 55 gallons for three fish
Lionhead Goldfish Tank Size
Lionheads are slower swimmers and do best with other fancy goldfish.
Recommended sizes:
- 20 gallons for one
- 40 gallons for two
- 55 gallons for three
Bubble Eye Goldfish Tank Size
Bubble Eye Goldfish require special consideration due to their delicate eye sacs.
A larger aquarium helps reduce injuries and stress.
Recommended sizes:
- 20 gallons for one
- 40 gallons for two
- 55 gallons for three
Avoid sharp decorations regardless of tank size.
How Many Goldfish Can Fit in a Tank?
A simple guideline for fancy goldfish is:
| Tank Size | Fancy Goldfish |
| 20 gallons | 1 |
| 40 gallons | 2 |
| 55 gallons | 3 |
| 75 gallons | 4–5 |
| 90 gallons | 5–6 |
This assumes:
- Strong filtration
- Weekly maintenance
- Healthy adult fish
Are Goldfish Bowls Good?
No.
Modern fishkeeping standards no longer recommend bowls for goldfish.
Most bowls:
- Hold too little water
- Lack filtration
- Provide poor oxygen exchange
- Cause unstable water conditions
Even a small aquarium is a much better choice.
Does a Bigger Tank Make Goldfish Grow Larger?
This is one of the biggest myths in fishkeeping.
Goldfish do not stop growing because a tank is small.
Instead, poor conditions often lead to:
- Stunted growth
- Deformed bodies
- Shorter lifespans
- Health problems
Healthy goldfish grow according to their genetics.
Aquarium vs Pond
Some goldfish eventually outgrow most indoor aquariums.
Best for Aquariums
- Oranda
- Ranchu
- Fantail
- Black Moor
- Telescope
- Lionhead
- Bubble Eye
Best for Ponds
- Common Goldfish
- Comet Goldfish
- Shubunkin Goldfish
Ponds provide far more swimming space and often allow fish to reach their full size.
Common Tank Size Mistakes
Avoid these common errors:
- Keeping goldfish in bowls
- Following outdated “one gallon per fish” rules
- Buying tanks based on current fish size
- Ignoring adult size
- Overcrowding
- Underestimating waste production
Frequently Asked Questions
What size tank does one goldfish need?
Most fancy goldfish need at least 20 gallons, while Common Goldfish need 55 gallons or more.
Can two goldfish live in a 20-gallon tank?
No. A 20-gallon tank is generally suitable for only one fancy goldfish.
Is a 10-gallon tank okay for a goldfish?
No. Even the smallest fancy goldfish eventually need more space.
Do goldfish grow to the size of their tank?
No. Small tanks often cause stunting and health problems rather than healthy growth control.
What is the best tank size for beginners?
A 40-gallon aquarium is one of the best choices because it provides flexibility and stable water conditions.
