220 VAC parts controlled via 12 VDC pump
Heater elements take a significant current, but a contactor with a 12V coil would be the simplest option.

Gas powered furnaces have safety interlocks to ensure that the burners don't keep burning in the event of loss of exhaust fan flow, and this is done with a pressure switch, in which a microswitch is operated by a diaphragm. If you used something like this you'd be able to shut off the heaters even if the pump continued to have power but had failed - seized, broken impeller etc. This would still require you to use a contactor to deal with the current requirement, and to switch the coil with the pressure switch.

It all depends on just how much safety protection you need. Hopefully you also have safety thermostats in the heater vessels too as a last resort.