You have a couple of options. As already listed you can glue Velcro to each part and use a Velcro or similar strap. If the tanks are Kevlar or fiberglass you can glue tabs onto the tanks that correspond to brackets on the fuse and use a small bolt. I've set up tanks where I glued a tab at the back that engaged a slot in a former or other structure then bonded a block of wood on the front that had a little aluminum angle bracket that aligned with a block glued to the fuse. For plastic tanks I like to add a couple small dabs of E6000 to the bottom of the tank so it doesn't slide, and use a couple long tie wraps.