Using Copper Wire vs Type K Thermocouple Wire for PID Controller Connections

I am using a PID temperature controler to regualate water temp in a 90 gallon tank.
After fabricating a prototype, I realized the need to be able to quickly plug & unplug the unit and remove it. For testing purposes, I have attached the thermocouples directly on the PID unit but I will need to install the proper type K thermocouple plugs.

My question is will I need to use thermocouple wire to go from the PID unit to the female plug or can I just use stranded coppper wire. I did some reading and have found that a cheap chrome plug plut can not be used; only a thermocoulple plug but do I have to use thermocouple wire for the lead from the unit to the 1st half of the plug?


Thanks for any input.