Refractometer same as basic Seatest needle arm

[mavjoy]

I finally purchased a Refractometer today and got it calibrated. I've been using a Seatest needle arm hydrometer for the past 4 months on my 10 gallon reef tank and I wasn't sure if it was accurate. I put the refractometer to the test and hold and behold, the hydrometer was almost the same as the refractometer! I spent $50 and my cheapy hydrometer was giving me accurate results LOL. Oh well, i guess i could always use both of them and compare results to be sure of my SG.

[scarfish]

The hydrometer is garbage, the smallest amount of salt on the arm will eventually give you a false reading. Good refractometers will come calibrated also.

[HankB]

IMO well worth the peace of mind knowing that your SG is correct. Going forward, I suspect that the refractometer is easier to use and less likely to give you a bad reading.

 

Do the same with thermometers: RAIT == Redundant Array of Inexpensive Thermometers. Or you can spend the $$$ to get a good lab grade alcohol thermometer to cross check your tank thermometer. It's not uncommon for hobby thermometers to be off several degrees or more. Along with that, get used to how various tank temperatures feel to your bare hand as you can also double check that way.

 

And watch that heater in your RSM as a lot of us have already replaced ours due to poor temperature control.

 

-hank