For beginners, testing your aquariums water parameters can be one of the most interesting and important ways to see what is going on in your reef. Whether it be monitoring your tank cycle or keeping track of various parameters such as calcium or alkalinity, test kits are one of the most important pieces of equipment a reefer can have on hand.

Hydrometers and refractometers are both used to measure salinity so why the big difference in price.  A hydrometer is a great piece of equipment, its relatively inexpensive and easy to use, however over time they can become less accurate in measuring your salinity, which can have drastic effects on your reef.  A refractometer is a more precise is able to be calibrated on a regular basis.   For the short term, a hydrometer is sufficient but in the long term, a refractometer is an excellent investment you won't regret.