I know what most, and rightfully so, will say about this in regards to the chosen adhesive... use a silicone aquarium safe glue.
Now here me out, I understand, that is in the plans for the future when this experiment is found to be successful and I upgrade to a much larger tank. This is just trial and error.
I have read several times that people out there have found it successful to use hot glue guns to adhere things that go into their aquariums. I already own a hot