You can put anything in a fish tank, assuming you can find a big enough fish tank. What happens after that can vary. If it is made well, it shouldn't come apart, but i don't know how it would affect the fish.
I would not put the flower in the tank. The glue and tape will start to deteriorate and it could harm the fish. If the tank is against a wall, figure our a good placement for it, and adhere it to the back, outside of the tank. You will still be able to see it as you are looking through water. Almost the same effect as putting it in.