help please refractometer

[newman]

just buying one, what should be the correct SG for F8 PUFFERS also do i just need a salt water refractometer , thanks

[newman]

whats the difference between hydrometer and refractometer,

[Nick]

How they work. Refractometers are easier to read, and usually better calibrated out of the box as they are more expensive. They read SG by refraction. Hydrometers you have to get an eye for reading, especially the bobing kind, which must be used outside the tank in a still pitcher of water and not against the side of the container. Cheap innaccruate hydrometers are more common. They use the density of water at a specific temperature to measure SG, and as a result, you must also make sure the water is at the correct temperature for the reading to be accurate.

[Nick]

F8 puffers should be kept at SG 1.005.

[Boxermom]

There are a large number of different types of refractometers. If you get one, make sure it is to measure SALINITY. Not all do. We recommend F8s in 1.005-1.008, but the variance is negligible really at those levels, so anywhere in between there is fine.