Quote Originally Posted by Wateveryousay View Post
Does a refractometer measure different things, how is it different from a hydrometer? Do I need a Protein Skimmer?
A refractometer uses light through a small water sample to measure light. A hydrometer uses buoyancy. A refractometer is easier to calibrate and more accurate. A hydrometer can be thrown off by things as simple as bubbles in the water collecting on the arm. You tend to calibrate hydrometers by figuring out how inaccurate they are and adjusting for it.

Whether or not you need a protein skimmer is a touchy subject. Most will say "yes" or at least "if you keep corals". In reality it is a lot more complicated. It tends to be a balance of bioload and how sensitive the corals are. Fish-only, no skimmer needed. Corals that don't mind nitrates and so phosphates, skimmer may not be needed. SPS reef tank, skimmer likely to be needed.