The Goldfish Tank Size Calculator helps fish keepers determine the right tank size for their goldfish depending on the type and number of fish they plan to keep. Goldfish are often misunderstood as small bowl pets, but in reality, they need large spaces to grow healthy and live long lives. This calculator is a useful tool because it removes the guesswork and provides an accurate water volume requirement.
This calculator belongs to the pet care and aquarium category. It is designed for aquarium hobbyists, beginners, and anyone planning to keep goldfish in a safe and healthy environment.
formula
Formulas for Fancy Goldfish
(e.g., Oranda, Fantail, Ryukin)
Base tank size for one fancy goldfish:
20 gallons
Additional volume for each extra fancy goldfish:
10 gallons
Calculation Formula for Total Tank Size:
Total Gallons = 20 + (10 * (Number of Goldfish - 1))
Formulas for Common / Single-Tail Goldfish
(e.g., Common, Comet, Shubunkin)
Base tank size for one common goldfish:
40 gallons
Additional volume for each extra common goldfish:
12 gallons
Calculation Formula for Total Tank Size:
Total Gallons = 40 + (12 * (Number of Goldfish - 1))
Helpful Reference Table
The following table shows general tank size requirements for quick reference. This helps aquarists plan without calculating every time.
| Type of Goldfish | Number of Goldfish | Minimum Tank Size (Gallons) |
|---|---|---|
| Fancy Goldfish | 1 | 20 |
| Fancy Goldfish | 2 | 30 |
| Fancy Goldfish | 3 | 40 |
| Fancy Goldfish | 5 | 60 |
| Common Goldfish | 1 | 40 |
| Common Goldfish | 2 | 52 |
| Common Goldfish | 3 | 64 |
| Common Goldfish | 5 | 88 |
This table shows that fancy goldfish need less space compared to common goldfish, which grow larger and swim more actively.
Example
Suppose you plan to keep 3 fancy goldfish.
Step 1: Use the formula Total Gallons = 20 + (10 * (Number of Goldfish - 1))
Total Gallons = 20 + (10 * (3 - 1))
Total Gallons = 20 + 20
Total Gallons = 40 gallons
So, for 3 fancy goldfish, you will need at least a 40-gallon tank.
Most Common FAQs
Goldfish produce a lot of waste, which quickly pollutes small bowls. Without enough water volume and filtration, toxins build up, causing stress and early death.
Yes, fancy goldfish are smaller and slower swimmers, so they need less space compared to common or comet goldfish, which grow larger and swim actively.
It depends. Goldfish are best kept with other goldfish. They have different temperature and care needs than tropical fish, so mixing them with other species often causes health and compatibility issues.