13mm O/D to 3/8" I/D Tubing coupler

thingiverse

I use this in my fish tanks for sump pump to auto-level my water and also for aquaponics to pump water through my plant beds. This is a coupler-reducer for small aquarium pumps connecting 3/8 inch black vinyl tubing securely. The slight reduction on the inlet to the larger tubing helps prevent hydro-lock on my bell siphons due to decreased flow rates, while the coupler ensures a snug fit between the pump and 3/8 inch tubing. I found that the coupler that came with the pump didn't fit the 3/8 inch tubing tightly enough, so I tried plugging the tube directly into the pump but there was still a one millimeter gap.