hydrometers

[sjfishguy]

Great point about temperature! The amount of water used in a refractometer (a drop or two) is so small, that it is calibrated at room temperature. For example, your tank is 80oF. You take out two drops and put them on your refractometer- it takes less than 30 seconds for the water temp to reach the temp of the refractometer. You calibrated it at the same temp (room temp) and therefore you now have an ACCURATE specific gravity reading. Temperature changes the density of water, and saltwater for that matter, so you must take readings at a the same temperature at which your instument was calibrated. So your "paperwork" says it is accurate at 77oF (I still dont know why I need paperwork, but whatever), but at any other temperature, its off. You can do a conversion or let the large volume of water (relative to two drops) to cool to room temperature, or you can get a refractometer.

And if you say a a hydrometer, esp a floating one, is easier to use than a refractometer, I agree, you have never used both.

 

[coolfishy101]

Ok, you caught me lol, I never have used a refractometer (although I have seen one used, but that really doesn't matter) Both are actually really easy to use saying one is easier is like saying a 1lb weight is easier to lift than a 2lb weight, it may be true but both are still very easy to lift. It doesn't take very long to test salinity/specific gravity either, with either instrument (same thing, one may be faster, but only like 5 seconds faster...who cares?).

But, the true argument here is the accuracy of the instrument, not the ease of use. Both sides have arguments, but no SOLID evidence. I wonder if maybe my swing arm hydrometers are all off the same amount? My corals and fish look very healthy and I'm getting great growth but i don't know?

p.s. This thread seems to be getting a little heated, so lets try to relax a bit...