It's a new tank, and it has a betta. That's why TSS+ was used.DutchAquarium said:firstly, you don't do 100% changes, maybe 10% a week. Your going to need to wait 4 weeks now for the levels to stabalize. You need a reading of 0 for ammonia in your aquarium. Hopefully, you don't have anything in your aquarium right now other than decorations and water. If not, get the fish out. Ammonia is toxic at this level.