If you can afford the best way to go IMO is a good refractometer. I used the swing arm hydrometer for about 3 days then threw it out the window. Was to inaccurate. Plus the tiniest air bubble would throw the arm off. This was one of the first things that I invested in. Plus mine is temperature calibrated so i don't have to fuddle and guess if my tank temp is low or high. A few drops of water on the glass prizm close the lid hold the instrument up to the light and you have a pretty accurate reading. One thing I found out while researching refractometers is they are used also to measure the ripeness of fruit, alcohol content in wine, the brine in pickles was pretty interesting. Anyway as you can see by my posts I have limited experience in this hobby but IMO a good refractometer is the way to go.