it shouldn't cause an ammonia spike, especially if the tank is fully cycled. You can leave it in and it will dissappear in a few days. If you don't like the way it looks... take it out.
No it will not cause an ammnonia spike, I always leave mine in for the inverts to eat, but if it is not gone in a couple of days then I would remove it but it won't cause any harm yo your tank if you leave it in.