Man.....that does suck......sorry about your luck......
Most homeowners insurance will pay for cost of cleanup and equipment loss and damage, but as far as livestock and such I find that rather hard to believe.....Most policies have clauses plain as day, that they don't cover mamals, birds, fish, etc.......I've even gone so far as to get an Inland Marine policy, and that's iffy........
Regardless a terrible thing.....Are you sure you didn't have a rock slide or something fall in that area? Possibly might have been knocked during room renovations......It's possible with the tank sitting on the carpet that did have some affect or cause undue stress????
Most people will advise strongly against setting a tank up on carpet due to the padding and such compacting over time causing a shift.
As far as AGA honestly taking blame for something like this????
fat chance......Contact your homeowners, and see what they'll cover, and don't give up on the hobby......Maybe just take a break and reevaluate things, and come back strong........