Go to Tap Plastics and get the epoxy that is for casting stuff in. They even have videos on YouTube showing you how to do it. I would make an acrylic try put all the casing in it and pour in epoxy, pretty easy. Or go with the other idea of making a panel under and behind the tank and fill that with the shells, that would be just as easy and you would never have to worry about the water contact issue. You could get them nickle platted, it probably would not cost that much and it would look sweet but would not have the brass look obviously.
