Small overflow questions

[baywindow]

I have some overflow questions, and would be grateful for some advice. I'm planning an overflow across the full length of the (glass) tank, and an external box siliconed on the side. Bean-animal in the box. I've seen mainly that people drill holes between the tank and the box.

My thinking is that I could just have a small cutout at the top of the glass to let water flow between the aquarium and the box.
Also: I mainly see large overflows on pictures. Can I do a small overflow?
Either an L shape 1 inch x 1 inch or a 45 degree 1.5 inch? Any advantage/problems? 45 or L, which is best?
And finally, is there a minimum distance between the top rim of the aquarium and the highest point of the overflow? 1/2 inch enough?

Or with a 45 degree angle

 

[DSEKULA]

Usually an over flow is connected with a bulk head not just a hole, you drill the holes to match and the bulkhead allows water to pass from the tank to the box and also holds the box in place. If you want to make the connection with only silicone that box would need to extend all the way to the bottom of the tank and be supported by the stand. Do you have experience cutting glass to make those cuts? Doing cuts like that will take more skill than a simple hole or a couple. I'd recommend a stationary wet saw with diamond blade. You'd also want to do the cut before the tank was assembled or disassemble the tank and reassemble after otherwise I'm not sure how you'd manage to get it under the saw. You can do a small overflow but the reason the most saught after is a large one is that it leaves the least amount of dead spots.

 

[RocketEngineer]

Having an overflow that is long but doesn’t protrude into the tank much is what I had in my last tank. I bought a used tank so had to work around existing holes. The problem you run into is cutting the slot in the top of the glass is very difficult. There are ways to do it but they are risky or expensive. Instead, I’ve seen entire panels that act as the overflow lip and an external box for all plumbing. This is how Melev set up his 400g.

Using just silicone to bond the outside box to the tank is fine for a glass box. Idid that with mine but added gussets you be safe. Supporting the plumbing helps.

 

[RocketEngineer]

 

[RocketEngineer]

That’s about the best image I have. You can see the thin internal box, the two holes I had to work around. And the external box.

 

[baywindow]

Thanks a lot. Yes maybe a thin but deeper with two holes is an alternative. Also I could see Melevs 400g setup on this video, good stuff.
But I cant make the overflow box extend the whole side since it will be partly inside a stone wall.

An idea to avoid cutting the slot is to just have a lower glass, and two smaller piece say 1 inch high on the left and right side glued wih silicone. As I see it there will be very little pressure from water on these small pieces since the actual overflow inside the tank is the part taking the pressure.

But maybe thin and deeper is a better alternative since it is done before.