Hydrometer Use

[zackish]

Today I learned a very good lesson on hydrometers while setting up my first SW tank. I learned why they can be so innaccurate but they can be accurate if you take a certain step.
I found myself beating the hydrometer more than I was reading it to get the air bubbles out. The air bubbles are what can make the hydrometer very innacurate. If there is even 3 decent sized air bubbles on your needle it will bring your needle all the way up to the top.
You can avoid this by simply banging on the sides of the hydrometer or tapping at the plastic front of it. The bubbles will slowly come off and finally it will give you an accurate reading. You want all the bubbles to be off because even very very small ones can make a .01 of a difference. I had 2 very small bubbles on the needle almost invisible. I kept hitting at the plastic until they finally released and my needle dropped from 1.023 to 1.022.
Don't be afraid to hit your hydrometer hard with your hand either because it is hard plastic. You won't break it.
I just thought I would give everyone a heads up on that because I think it's very important. The air bubbles are most likely why everyone claims that hydrometers are inaccurate. Now I am sure a refractometer is much more accurate but if anyone like myself just goes out and purchases a instant ocean or corallife hydrometer then you can get away with accurate readings by the above steps.
I don't really think this is worthy of a sticky but it would be nice if everyone who wanted to know a little bit about hydrometers was able to read this. I promise you if all the air bubbles are off the needle it will give you a steady reading.

[cocoa_pleco]

i screwed up my first hydrometer use years ago. i read it upside down and i added about 55g worth of salt into a 10g and was like "the fricken needle isnt moving!" nevertheless, i had to add alot of FW to balance it.

and yes, dont be afraid to slap the hydrometer and wash it in hot water, mine still works from 4 years ago