How long has the tank been set?
I receommend the following:
After putting in stuff to help cycle (whatever it was), Test once a week. After that test, do a water change.
Same day next week, test again. Do same amount of water change
3rd Week, same thing test same day and same amount of water change.
4 week test. If that 4th week is on a downward cycle, wait one more week. Test, do water change and then test again after the full amount of water change has had time to cycle through. Evaluate from there if it's worth adding inverts/animals etc.
House