Fritz 35 PPT Calibration Fluid

Fritz 35 PPT Calibration Fluid is a precise salinity standard that keeps your refractometer or hydrometer reading accurately. Set to 35 parts per thousand, the salinity of natural seawater, it lets you calibrate your salinity tester so you can trust every reading and keep your saltwater tank in the right range.

Why Calibrate

• Sets your refractometer or hydrometer to a known standard
• 35 PPT matches natural seawater (1.0264 specific gravity)
• Ensures accurate, repeatable salinity readings
• Cheap insurance against a drifting instrument
• A reef-keeping essential for stable salinity

How to Use

• Make sure the refractometer prism is clean and dry
• Place 2 to 3 drops of the fluid on the prism
• Adjust the calibration screw until it reads 35 PPT (1.0264 specific gravity, 1.3394 refractive index)
• Rinse and dry the instrument afterward, and recheck about once a month

Specifications

Pair It With

• Calibrate a salinity refractometer
• Or check salinity with an Instant Ocean hydrometer
• Browse more testing gear

Frequently Asked Questions

What does 35 PPT mean?
It is the salinity of natural seawater, about 1.0264 specific gravity. Calibrating your instrument to it makes your readings accurate.

How do I use it?
Put 2 to 3 drops on a clean, dry prism and adjust the instrument to read 35 PPT.

How often should I calibrate?
Checking about once a month keeps your salinity readings reliable.