It depends on how paranoid you are of something bad happening. If it were me personally, I would just put a 1ft - 2ft piece of pvc
on the end of it and let it hang in my sump. But then again I don't really worry about things moving and becoming dislodged because I'm the only one that touches my tanks.
You could also:
Make a stand with eggcrate, cut the cover down, and attach it to the eggcrate making a stand in your sump.
Remove the washing machine hose and just hard plumb it all (my favorite)
Make a bracket that will attach onto the side of the tank and will be able to secure the plumbing. You could even do this with some pvc
fittings to make it super easy
I have some other thoughts but they would have to be drawn out to make sense
There's a ton of things you can do... It's just how much effort you want to put into it and how creative you are