I'm using a electric density meter that calbrates for the temp. I got it from our lab at work. Anton paar density meter, new out of the package so there was no contaminents.
Keeping the sg at 1.009 is a chore it varies from 1.0092 to 1.0102. I have them in a smoll room by themselves so traffic would be minimal. Do you think the ac in a small room is a factor as far as temp swings? Yes, I have a heater.