This is the start of a project to have a modular system for rimmed tanks for holding anything need to hang on the side of your rimmed tank. 

Currently, this system is only the plant holder, which can hold rooted plant trimmings, or even hydroponic substrate with plants. This bracket setup will fit rimmed tanks ranging from 120, 75, 60, 55, 20, and 10 gallon tanks (Most are Aqueon brands).

The goal is to eventually have multiple detachable components so you don't need to have another bracket just to add something new to the tank. 

For printing I had the best luck with speed/quality by printing the bracket on it's side with manual tree supports on the inside of the dovetail. You can print it upright and use supports, but it takes longer and uses more filament.