We have developed this re-usable 24-well glass microplate for high through-put respiration measurements in tiny aquatic organisms. Each well is fitted with an oxygen sensor spot allowing for non-invasive optical oxygen measurements when placing the microplate on a special reader. By placing a soft silicone gasket lined with a thin gas-tight film (e.g. PCR film) a gas-tight seal is formed for respiration measurements inside the wells at any environmental temperature. The sensor spots and glass microplate can be cleaned with chlorine, ethanol etc. between trials and re-calibrated and thus used again and again.