Overflow in non-drilled tank

[Recife]

My tank is not drilled and I'm considering different options of draining water down to the sump. The other problem with the tank is that the top only has those 2 big openings on the center of the top and none close to the back wall of the tank. If it wasn't for that, I would use an external overflow box.

Can you give me your thoughts on these options?

1) Drill an opening on the top of the tank so I can sit an external overflow box in it. This would be my personal favorite.

2) Try and extend the external overflow box so it will each the opening in the center of the top.

3) Drill a hole on the back wall, add a bulhead and a pipe facing up to drain the water (I heard this can be noisy and would have a smaller flow than an overflow box.)

4) Is it possible to use a pump to send the water down without drilling or using an overflow box?

Thanks :)

[TekCat]

1) Way to go
2) too much unnecessary plumbing
3) Way to go (Peice of mind, not worrying that siphon might be broken)
4) Definate NO! You wont be able to control amount of water coming back up to offset water that you pump down. i.e. flooding

[Lakeside518]

Is this an acrylic tank? Sounds as tho you will need to drill it if its not reef ready? Add bulkheads or build your own internal overflow and drill tank.

[philagothos]

My vote is for option 3b. #1 could weaken the integrity of the tank and cause big trouble in the future. #2 sounds feasible, but could be a challenge. #4 would be ugly and you would have to exactly match the flow with your sump return pump, or have a big wet mess.

For 3b, I would make a small overflow box on the back so that you can use a stockman or durso drain. That way you don't have to worry about the noise. Also, this can certainly flow as much as any external box, you just need to make sure you use the right sized drain tube.