It appears to be impossible to do what Aqueon suggested, the threads are 1/2" larger in diameter than the hose itself, stretching PVC
hose to twice it's own diameter is not that easy. I've returned the water changer and ordered a Marina Clean no spill changer system instead. It appears to have the hose permanently attached to the gravel tube with the hose screwing together further down. it looks more reliable, plus it has brass fittings and an 18" gravel tube instead of the 11" Aqueon. Only $10 more. Basically identical design to the Python, just a different brand.
Thanks for the help anyway everyone.