I used US Composites marine epoxy and 3 layers of fiberglass 7oz for the base water proofing. And then Applied 4 coats of sweet water epoxy. I did all of this while all the pieces were apart. Then once all coatings are setup, not longer tacky, I put all of the sides up and bolted and lag screwed everything together along all corners and along the bottoms of each panel. Then using the calking tool, I have a picture of it in my gallery, I put a very thick bead of calking in all of the corners. It worked so well From day one of filling it I haven't had a single leak. I've had the tank up an running for about a 2 months