Hypo Hydrometer Problems...

[eipappas]

So I am at the critical stages in reaching hypo in my QT... I managed to get the tank down to what I thought was 1.012 (or so it says on my plastic swing-arm hydrometer)... but I just bought a glass hydrometer (kind of a dinky one though - it was all the LFS had) and it reads 1.010...
How can I tell which one is right? How essential is it that I am at exactly 1.009?...
Also - Once I'm at 1.009 - How do I make water changes? With pre-mixed saltwater at 1.009??
Thanks!
Elena

 

[dburr]

Take both hydrometers to the store with some of your tank water and some new water you mix up at what you believe is 1.009.
Have them check the water samples with their refractometer.
They will tell you how far off you hydrometers are and you can make your corrections.
Example: My deep six is reading .0018 off at 1.025 at 79 degrees.
So I make new salt at 1.0232 which is really 1.025.
At 1.009 my deep six reads 1.009!. How do I know? MY LFS checked a batch of salt I made.
My fish have been in hypo for a week and are doing great.
I do 1.009 water changes every 3 days, and check the water params every other.
HTH