Briefly, the present disclosure provides a device comprising: a) an LED capable of emitting light at a first wavelength; b) a re-emitting semiconductor construction which comprises a potential well not located within a pn junction; and c) a reflector positioned to reflect light emitted from the LED onto the re-emitting semiconductor construction. The filling element contains a flexible hose, which extends right to the base of the tank and which at the free end has an axial outlet orifice directed towards the base of the tank. Parts of the pacemaker are coated with a material, in particular a nanostructured material, which counteracts magnetic effects.