I’ve done it a couple times with no problems.
However:
I had tubs ready for Incase I cracked while drilling. I had 50+ holes under my belt before I felt comfortable doing this on a cycled tank in use. If you have glass drilling experience, you probably wouldn’t be asking this, but if you try, go slow, be gentle, take your time, and have a plan if you crack it. I’ve done it, it can be done, but it comes with risk. Light pressure, it takes time, and be gentle. I used painters tape and plastic to keep the drilling fragments out of the water. And keep it wet at all times, I used an aqua lifter (and another person to keep it pumping on the bit) to constantly pump water on the bit. With the right bit and patience it’s not too hard. But if you try it, make sure you have a back up plan for the tank if it cracks.
However:
I had tubs ready for Incase I cracked while drilling. I had 50+ holes under my belt before I felt comfortable doing this on a cycled tank in use. If you have glass drilling experience, you probably wouldn’t be asking this, but if you try, go slow, be gentle, take your time, and have a plan if you crack it. I’ve done it, it can be done, but it comes with risk. Light pressure, it takes time, and be gentle. I used painters tape and plastic to keep the drilling fragments out of the water. And keep it wet at all times, I used an aqua lifter (and another person to keep it pumping on the bit) to constantly pump water on the bit. With the right bit and patience it’s not too hard. But if you try it, make sure you have a back up plan for the tank if it cracks.