Hydrometer readings
 

Just wanted to know something from the experience of people who used both hydrometer and refractometer. Hydrometer do give inaccurate reading but is it above or below the actual SG?

It could be either, depending on the hydrometer. You should get yours checked against an accurate refractometer to know exactly how far off, and in which direction your hydrometer reading is.

However, over time it could change. Just buy a refractometer :)

Yah I will but not until the end of August since I will be away for this whole month. My room mate will take care of my tank by feeding the fishes and doing a cup of fresh water top-off every two/three days. So just wanted to make sure that I am getting approximately correct results using the hydrometer so that I can tell him the interval of the top off. I always clean my hydrometer with warm water and vinegar after every use. Any suggestion? :question:

Take it to an LFS and get them to check it for you. I've personally seen them inaccurate by as much as 0.008 in either direction.

Yah I was thinking of doing that along with the other parameters too. Any idea how much water I should take to LFS?

100 mL is usually plenty.

I had mine tested as being almost completely accurate. It stayed that way for years, until it changed, and by a lot. I ended up running a tank at 1.032 for 4 months. It caused me a lot of grief..

Great :D I was thinking like a liter or something :P Silly me!

4 months? :O That's a long time! So does that means a "out of the scale" salinity will actually take a long time to punch the system?