If you don't get anywhere through your insurance company, I think i'd still give them a call myself, explain the situation, offer to send pics, and see if they will offer any remedy. You might mention that some people on "all the internet forums you regularly post on" thought they might help you (or some creative way to say "I'll tell everyone your tank broke")
Worst case you waste 15 minutes on the phone and are certain you did everything you could. It totally sounds like a defective build to me.