Yes hospitals and labs will be calibrated as accuracy and repeatability is key.
As for fish keeping, +-1 'C (or more will be fine), fish won't mind.
Personally I would stick with a liquid in glass thermometer designed for fish tank use. It will have been designed for limited tank water range, so liable to be more accurate than a general purpose large range thermometer (ie -20 to +90 for instance). Also big plus no batteries required, all adding to the KISS of fish keeping (Keep It Simple Stupid).
As for fish keeping, +-1 'C (or more will be fine), fish won't mind.
Personally I would stick with a liquid in glass thermometer designed for fish tank use. It will have been designed for limited tank water range, so liable to be more accurate than a general purpose large range thermometer (ie -20 to +90 for instance). Also big plus no batteries required, all adding to the KISS of fish keeping (Keep It Simple Stupid).
