When dealing with smaller tanks I think a refractometer is necessary. A ballpark number can be deadly in a small enough tank.
In larger tanks I agree it isnt a necessity, but since a hydrometer is like $10 and a refractometer is $30 why not spend the extra $20 to get the accuracy? I guess it's what your budget can take. lol
180g Reef - 60g Rimless Reef -90G FOWLR- 125g Malawi Cichlids- 40b REEF- 34g Fresh Planted-working on- 20L FOWLR- working on
I have a mix of many different saltwater fish amongst my tanks, but I love my Tangs most of all.