Hehe. Well, they won't leak - it is VERY thick plastic and it needs to be considering the chemical that is in the glass tube that you break when you snap the glow stick. The chemical in that tube is toxic, but it won't kill you since children use glow sticks and chew on them sometimes. The chemical in that glass tube stains plastic if that is any indication of what it will do and I believe it can slowly dissolve certain other plastics. However, the other liquid that is simply in the plastic tube when you buy the glow stick is hydrogen peroxide in some kind of oil that makes it a bit viscous (I don't know why they do that).
Basically, as long as you aren't cutting them open with sharp, strong scissors and pouring them into your fountain, don't worry about it. You won't have any problems and it will look very cool!
BTW, yes, as someone mentioned, they are sold to divers.
I don't know if it is a semi-local store or not, but Chase Pitkin has some good glow sticks for a reasonable price. Very bright and long lasting. I think they are only in neon green or orange though. However, there are places that sell red, blue, etc.
Enjoy.