Yes, it appears that most super glues (cyanoacrylate) are water-stable and aquarium safe. I would only use regular super glue, none of the specialty types like rubberized CA
, etc. The few times I've used it, I let the glue cure for at least 24 hours just for my own personal assurance that any outgassing had finished. Keep in mind that CA
itself is relatively brittle. For larger or heavier objects you wish to join I would suggest using aquarium-safe silicone. Then there's epoxy, the power-geek, DIY'er adhesive of choice.