When the tank is cycling, you keep it at the usual temperature, between 24 and 26c (67-69ish in old money)
Does your refractometer have Automatic Temperature Correction build in? If not, you'll have to calibrate it from calibration solution at the tank's temperature If the refractometer has ATC you can calibrate it at room temperature if you allow it 30 seconds or so to adjust for you
HTH
Rabbut
sorry you have lost me know, it hasn't got an automatic temperature correction, but it tell you to give it 30 seconds for the temperature. Does this mean the reading i get, is the actual correct figure?
also i've just done an ammonia test and it was between 0.25 and 0.5, is that normal for the start of a cycle?