When I bought neon tetras, I bought 40 small neons (which was not a good idea). I think I crashed my cycle when I added 40 of them in the same time. They got NTD the following day. One week later, they are 30. One week later, they are 20. After one month they stopped dying. And after one week they are 10. And now they are only 9. They stopped dying again recently and their colors came back. Are the spores of NTD are still in the tank? Am I safe of adding new fish again?