Hydrometer.

[tarvis]

I second that

 

[bertoni]

I used a floating hydrometer for years. As long as you calibrate it, it should be okay, but they're a pain to use get dirty, and you need to draw a large sample into a graduated cylinder (or something similar) to get a reasonable reading.

 

[JoeRonda]

Cool thanks and it is a swing arm. I am going to look into the glass and like i said i am waiting until i get a little cash i jsut bought a RO DI unit and didn't want to tell the women i was spending another 100 on a refractometer. She would crap!

Go on BigAlsonline, I got a Milwaukee Instruments Refractometer for $59.99
that's their regular price, it might even be on sale. Put in "reeftank" in the coupon code at checkout to get a 10% off discount too.....

 

[spslove]

I used a floating hydrometer for years. As long as you calibrate it, it should be okay, but they're a pain to use get dirty, and you need to draw a large sample into a graduated cylinder (or something similar) to get a reasonable reading.

What kind did you have that you have to calibrate it? Mine is calibrated to 25 celsius. I cant calibrate it.

 

[bertoni]

Well, calibration in this case just means measuring a test sample, and recording its measured value, so that you can subtract or add the relevant amount when you take a measurement. Here's an article that describes how to make a calibration solution:

http://reefkeeping.com/issues/2004-06/rhf/index.htm