The drilled hole is used for the overflow to connect to the drain pipe via a bulkhead. When drilling a hole you will need to factor in its location as the height of the drainpipe within the overflow will dictate the height of the overflow in the tank. This then dictates the height of the water level in the main tank.
How do you plumb a drilled aquarium?
https://www.youtube.com/watch?v=sH5mq3P3tEY
Do saltwater tanks need to be drilled?
No you do not need a drilled tank. They drill tanks to make it easier for overflow filtration systems i.e. sump, wet/dry, refugium, etc.
How do you tell if you can drill an aquarium?
https://www.youtube.com/watch?v=O3J47iP1KKM
Can you drill holes in a fish tank?
Drilling a glass aquarium is loud and potentially messy. So make sure you invest in proper safety equipment. And take the time to make these preparations. It'll save you some of the anxiety you may already feel.
Can you drill the side of an aquarium?
For the best possible result, you should drill the hole from both sides. It may take slightly longer, but if your goal is to do it right and get a clean hole with no chip-out, then it is the best method.13 Nov 2014
How do I know if my tank is tempered?
https://www.youtube.com/watch?v=1eKhF8YLK8U
How can you tell if an aquarium is safe?
https://www.youtube.com/watch?v=_s-WwDiWWkk
Can you drill the bottom of an aquarium?
I drilled the bottom of my tank and used it for closed loop. If thats what you want to do, then it should be no problem if done properly. It looks like that tank was drilled for one drain and two returns. you can use Sch80 heavy duty bulkheads and put good quality union valves and you are good to go.19 Jan 2018
How do you drill a hole in the bottom of a fish tank?