Drilling Established Tank

[byee]

I have an established 120 gallon reef tank for 5 years with a CPR overflow which uses an airlifter to maintain the siphoning.

I'm getting a VERY tired of the airlifter failure! Siphoning stops, the return pump continues to pump water out of the sump into the main tank....sensors in the sump senses a low water condition and my resovier pumps water into the sump........WET BASEMENT!

I'd like to drill the tank to install an overflow into my established tank. Has anyone attempted this on this forum? I can empty approximately 40-50% of the water. Will this work??

Thanks!