Hey, I've been working on a turtle platform and waterfall for my girlfriends 20gal aquarium, I've got the styrofoam (white type not the stronger pink building material) all ready to go for concrete. I am using Quikcrete hydraulic water stop cement. Im not too educated about preferable types of cement here but maybe you guys have a better suggestion. Also i was worried about the turtles maybe damaging the dock so i was wondering whether or not i need to put a seal on it?? like Epoxy resin etc