Backyard Aquaponics
A place to discuss aquaponics

A gravel guard that allows you to get your hand down in to clean out roots and clogs is going to take about the same amount of space no matter if you use an internal or external siphon. Moving the siphon out of the bed doesn't really give you more grow bed space.

However, moving the siphon outside the bed does give you the benefit of NOT needing to thread a fitting in both sides of the existing bulkhead fitting.

I'm sure this has long ago been answered but i bought a 150 g rubbermaid with the same drainage fitting. It said it was 1 1/2 but i simply could not get a 1 1/2 in male to screw into that. It looked like it was really close however so i kept trying. With my full body weight and a little luck i finally got the threads to grab and was able to get it to thread but it was highly frustrating. Its not been machined quite to spec apparently.

Glad you got it and I'll cross my fingers that it doesn't leak. Dirt or junk in the threads will also sometimes cause difficulty threading these.