Swivel arms moving...... Solution

[Methamphetareef]

Instead of tapping and using a screw to stop the swivel arms from moving, I just threaded a zip tie through the center hole of the swivel arm and bracket, back up around and "cinched" it down. Then I trimmed off the excess zip tie. Can't even see it.

This keeps the serrations firmly meshed.

If you want to change the angle, you will have to cut the zip tie, adjust angle and use another zip tie.

 

[Tremelle]

I bought a 1 1/2" long x 1/4" wide nylon screw. I then put a 5/16" washer on the head. I then ran the screw into the extension and bracket hole. Another 5/16" was then put on the screw followed by a 1/4" hex nut. It all worked perfectly. It is tight enough, and it still allows for adjustments by loosening the nut, repositioning it, and tightening the nut back. Here is a pic of it assemblied and mounted on the magnetic mounts.

 

[rvitko]

You can also put a piece of silicon airline (like the type on Euroreef skimmers) in the hole and then thread a 5mm screw (like the ones that come with the holder) into the airline. You need a washer as the screw head isn't wide enough. Any plastic plate would work.