Drilling a setup tank

[Afish70]

Is it possible to drill a tank that is currently up and running? I have a 90 gallon mixed reef and i want to drill it for an external overflow to also add a sump. What can i do?

 

[Reefer1978]

Is it possible to drill a tank that is currently up and running? I have a 90 gallon mixed reef and i want to drill it for an external overflow to also add a sump. What can i do?

Empty >> drill >> fill. I would not drill a running tank unless you would love an experience of instantly getting 90 gallons of salt water on your floor, right next to your electrical equipment you are using to drill the tank.

 

[NeonRabbit221B]

Has it been done? Yeah
Should you try it? No no no

The risk vs reward it pretty high unless you professionally drill tanks for a living as you are dealing with additional stress on the glass due to the water. You do not want to break a tank full of water.

 

[Redfoxtang]

I drilled my 60g with it running for 2 years. Basically I did above. Drain water, remove some rock, fish were still in system as well. Drill the tank then plumb and fill and it’s running till this day. No issues. But I did not put a weir. This is an external overflow.