Contolling Circulator Pump by water temperature

Hello,

I need to install a controller or aquastat that will turn on/off my recirculation pump which is connected to my tankless water heater with external storage tank. I am looking for reocommendations.

I am converting from an old boiler water to a high efficiency tankless unit (for commercial hot water). The new tankless unit heats water when it senses flow (unlike the old boiler). So when the water in the storage tank drops below about 110, I need the pump to turn on to create water flow to turn on the tankless unit. When the water temperature in the storage tank reaches about 130, I need it to turn off the pump to stop the tankless unit from firing.

I kind of get the idea a 3 function aquastat is what I need (hi, lo, diff) but any help would be appreciated. Also, does the immersion bulb funtion as the thermostat on such an aquastat? The old boiler had an aquastat and immersion bulb, but it was wired up to the burner only. The circulator runs/ran all the time to the boiler and storage tank loop

Oh, I the pump I want to contrl is an 1/6 hp lochinvar operating on 120v circuit.

Just wanted to update this with solution. I found a RANCO ETC-111000 which is like a digital version of an aquastat and includes a sensor. It is like a temparature controlled on/off switch.