[mike31154]

I have 3 hydrometers and 1 refractometer. One of the 3 hydros is the type you float in water and the other two are swing arm types. All 3 hydros came with used tanks that I purchased. The 'float in water' hydrometer appears to be more accurate than the two swing arm types and reads favourably when compared to the refractometer. In addition the float hydro has a built in thermometer. One thing to remember about hydrometers is they are not temperature compensated and since they are initially calibrated to read at a certain temperature, if you don't compensate, you will get inaccurate readings. Most refractometers are automatically temperature compensated, you just need to wait a few moments for the fluid to get to the same temperature as the refractometer glass.

I've seen on other boards that some folks recommend calibrating refractometers using a fluid (pinpoint usually) which is at 1.026 specific gravity. The reasoning being that this is where you want your refractometer to be most accurate and if you calibrate at zero, it's not a guarantee that it is accurate at the salinity range we usually check. I asked the question on that board if anyone had calibrated using the 1.026 fluid and then checked the zero with pure water to see if there was any error and never did get a satisfactory response. Personally, I calibrate at zero and have even found that it's almost impossible to see a difference at zero whether I use Vernon tap water or distilled water.

Since getting the refracto, I keep my water at around 1.024 on the refracto scale. I don't worry too much about a point or two difference. But I do make sure that when I perform a water change, the new water is as close as possible to the tank water. I check it two or three times to make sure since I tend to change a lot of water every 20 days or so vice smaller changes more frequently. Other than my fish, cuc, I have an anemone and a number of soft corals as well as a hammer and all the livestock seems fine with this level of salinity.