Here is the "drawing"...
I think it's kinda obvious how it works. If there are any questions, do not hesitate.
Obviously, the hot water outlet has to be connected to a hose and go into one or more reservoirs and return to the other connection (blue tube). As for the exposed part, a thick walled hose (plus insulation)- and for the part that goes into the reservoir, a rather thin walled hose is recommended. The water level at the secondary reservoir should be lower as shown (for illustration purposes only). To get the wanted temperature in the
nutrient reservoir(s) simply turn the knob until it reaches the wanted temp i
n the nutrient reservoir. The electronics of the heater then automatically regulates the temp - as both (heater and nutrient reservoir) are different, yet relational.