How to prevent overflow in main display tank?

[filipino]

First thank you for all the reefer shared their thoughts and ideas on refugium light question I asked last time. I really appreciate your time and effort and helping me since im new in the the hobby. This is the scenario, I recently purchase a lifereef overflow box and after waiting for long time it they have in stock and able to get what I ordered. (since some reefers told me this is the better overflow box considering the price of the unit). Now, " How I can prevent over flowing the Main display just incase the overflow box malfunction?" "Is there any device that will shut off the pump if detect the water level in DT increase?" Thank you in advance

 

[Hove75]

Have a shut off valve on your return pump... i think thats what your asking