This is where I think you should tell everyone what kinds of aquarium safe adhesives and caulking that you have used before, what you used them for and how well they worked. I just think it would be awesome for other people to know what types of things are safe to use in the aquariums we all dearly love. I have used GE silicone I 100% silicone rubber, I used it to hold together a pvc condo then to decorate it with rocks after wards. It is easy to work with and cures in 24 hours and sets in 30 minutes. Completely safe for your fishies, it is not mildew resistant. It also has a lifetime warranty

All I use is 100% silicone. As you stated Brisch, make sure it doesn't contain any mildew resistant chemicals by checking the label carefully.

Brand doesn't matter. I've used the GE stuff, I've used the el cheapo stuff from walmart. The only thing that matters is that it's 100% silicone with NOTHING else in it.