I've posted this before somewhere, but here's my situation directly from my Country Financial Rep regarding my home owner's policy.
If something catastrophic happened (tank giving way), they would cover all property damage. This includes the tank itself, any equipment, any water damage to the house, AND coral. He had to get some clarification because he initially did not know, but he found out that while they wouldn't cover the loss of fish because they are just animals, they would cover the loss of corals because they see them as property, not animals. He's been in the insurance industry forever and is certainly no slouch with intelligence, so I take him at his word.