A refractometer is a simple and robust way of accurately measuring the salinity within your aquarium and should be used by every serious marine aquarist.

Most people when entering the marine aquarium hobby tend to purchase a plastic swing arm hydrometer due to the low price of these items.

What many people are not aware or informed of is that this type of product can be notoriously inaccurate and can result in wild swings in salinity which is not normally discovered until there has been a system crash or livestock losses and the water is subsequently tested by a retailer.