Cheaper P&P via

Digital Thermometer

This thermometer is 13cm tall and 2cm wide and they stick to the outside of the tank and read the temperature.  It goes from 18 to 34 degrees centigrade (68-93 F) which will ensure you keep your instant pets at the optimum temperature.  It shows brown for 1 degree less, green the temperature highlighted is corrected and blue for one degree above.
 

Product Code: BS2
Price: £1.75