Here are the water quality reference ranges for the most common types of pet fish. Click here to find water quality requirements for more exotic fish species.

Goldfish (indoors & outdoors)

ParameterRange
Ammonia ≤ 0.1 mg/L (ppm)
Nitrite0 mg/L
Nitrate< 20 mg/L
pH6.5-9.0
kH (alkalinity)> 100 mg/L
gH (hardness)> 100 mg/L
Temperature32-85F (0-29C)

Koi

ParameterRange
Ammonia ≤ 0.1 mg/L (ppm)
Nitrite0 mg/L
Nitrate< 20 mg/L
pH6.5-9.0
kH (alkalinity)> 100 mg/L
gH (hardness)> 100 mg/L
Temperature32-85F (0-29C)
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Betta

ParameterRange
Ammonia ≤ 0.1 mg/L (ppm)
Nitrite0 mg/L
Nitrate< 20 mg/L
pH7.0-8.5
kH (alkalinity)> 100 mg/L
gH (hardness)> 100 mg/L
Temperature78-82F (25-28C)

General Tropicals

ParameterRange
Ammonia ≤ 0.1 mg/L (ppm)
Nitrite0 mg/L
Nitrate< 20 mg/L
pH7.0-8.5
kH (alkalinity)> 100 mg/L
gH (hardness)> 100 mg/L
Temperature78-82F (25-28C)

Please keep in mind these are general guidelines – not all fish read the book!