how glue?
1) WHY?
2) WHY?
and I wouldn't risk it how glue and stuff like that can be toxic. I'd stay with sillicone i know it takes longer to set but it's 100% safe (if you get aquatic sillicone)
Hot glue doesn't stay attached to the surface under water (speaking from a pool owner perpective) it tends to peal away from the surface after prolonged exposure to water. I used it on my pool latter and it started pealing away in under 5 hours plus I agree it is most likely toxic to the fish.
well to go against what some ppl are saying here, there is a non-toxic version of hot glue that i have used in my aquarium and have had no probs, ive never used aquarium sealent but im sure its better.