That is the overflow box that I have in the tank
That is the diy box I have mounted behind. It's just a plastic ice box I got at Target.
This is the part I was trying to describe in that icebox. The 2 big 1 1/2" bulkheads are fed water from the overflow box in the tank. In the ice box there are 3 bulkheads on the bottom. The middle is my full siphon. The one on the left is my secondary. And the 3rd is my emergency. The PVC
is about 1/4" taller then the one in the 2nd bulkhead. The middle bulkhead line has a ball valve further down. To tune it, I set the ball valve full open. Then I start closing it until the water level in the icebox rises to barely trickling into the secondary. And that's how I leave it running. It's extremely quiet. If I didn't have the secondary the middle one would take in air and there would be a loud gurgling sound.
This last pic is my filter under the tank. It's just a 3 drawer storage box that I also bought at Target. The top 2 trays are drilled with about 50 holes to form a drip tray. The bottom tray has a 3/4 bulkhead and a pipe going down into the water in my sump (which is a heavy duty storage bin that I bought from Lowes - 20+ gallons). This is to reduce the sound of heavy dripping into the eater in the sump.
It's currently not running because I'm working on cleaning up the routings and cementing the pipe together. But it does work and quite well.
The 1st tray will have porous sponges. The 2nd tray will have my bio-media. The 3rd tray will be completely loaded with filter floss.