No problem. Actually you may even add ammonia before it is 0ppm to make sure the bacteria won't starve for too long by the time you notice it is at 0ppm.
There is no need to get filter media from your neighbor's tank at this point. You have already developed both species of bacteria in your aquarium. A jump start is no longer needed. The biggest benefits of a bacteria seeding or transferring is to get both types of bacteria species at the very beginning. Without bacteria seeding, you will have to wait for the ammonia eating bacteria to develop first before there is nitrite for developing nitrite eating bacteria. By seeding both types of bacteria at the start, you skip the most time consuming part of fishless cycling.
I am a big fan of Thor too. Would you like to share some photos of your existing aquarium and fish? I want to take a look at your Thor haha!
