my diy overflow with standar pipe, 1/2 inch pipe
let me translate it for u:
kasih pipa kecil = add small pipe
lubang di sini= drill a hole for small pipe to in on to it, and seal it
atur batas yg di inginkan = end of the small pipe, make it straight with the end of U pipe
when the power head off, the water will flow to sump tank, but when the water level gets to the end of small pipe, air will enter the pipe and stop the water to the sump tank.
when the power head turn on agan, the water from sump tank fill the main tank, when the water level high enough, the water will enter the small pipe and the the water flow from main tank to sump tank is high, because no more air inside the pipe
u can use more larger pipe to get more heavy water flow
here how the aquarium it looks like