Will you actually be USING it externally? If you are going to sit it in your sump, I wouldn’t glue anything. Even if you are using it outside your stand (outside a sump), if you don’t want to glue anything, you can possibly sit it inside an old 5 or 10 gallon tank (or 5 gallon bucket) to catch minor drips/leaks. I’m just trying to spitball ideas in case you don’t want to glue it— which is fairly permanent.
I would glue any connection needed to remain water tight. external is the only way to go, been doing it, 20 years/ I use union connectors where I need to have a break for cleaning