Select a temperature controller and power relay, to be used to control a heater

I need a qualified industrial controls or electrical engineer to tell me the right way to do this. I don't need detailed drawings or renderings or anything, just a specification of the correct off-the-shelf parts that I can order and hand to an electrician to wire together. I have a large (750 L) saltwater aquarium heated with an inline heater in the water circulation system. The heater's built-in analog thermostat in the is not accurate or adjustable enough for our needs (we need +/- 0.1 C at 35 C). I'd like to supersede it by wiring a power relay in series with the heater's power supply, and use that to turn the heater on and off as required. I believe it's possible to connect the 12 V control signal from a cheap off-the-shelf thermo controller, like for instance an Inkbird Inkbird ITC-1000. What I don't know is if there are other parts required or features I need to worry about (I think I want a non-latching relay, for instance, but I'm at the limit of my knowledge here). The heater operates at 240 V, 30 A, so fairly beefy relay is required, and I don't want to mess around with that kind of current. Also I am not sure if additional control circuitry is required. The heater operates in a damp environment, and I am not sure if that adds additional requirements. What I want is a list of certified parts that I can order off-the-shelf in the USA, and a circuit diagram to hand to the electrician who puts it together for me. The heater model is: Coates 6ILS, [login to view URL] Please respond with your qualifications, and confirm your understanding of what the work product will be.