Nice to see that I am not alone.
I've used my 3D printer to print all sorts of stuff for my tank, including wave maker diffusers, a clone of Julian's thing, probe holders, enclosures for my DIY controller and dosing pumps, RSM media rack, etc.
DIY for me is 50% of the fun in this hobby and the 3D printer is a great tool. Just be aware they plug-and-play type of thing and many brands out there are well know for being unstable. Also, designing in 3D isn't something you will learn in a weeks time.
In theory ABS is the plastic of choice, because PLA would being organic would be consumed by bacterias. However, I have a couple of PLA parts submerged for about an year without any issues.
Also, I have black ABS, white ABS, grey PLA, blue PLA and my corals never complained.
I tried to put a link to some photos but the forum didn't let me.