If you've put Ammo Chips in the gravel bed, I think you need to replace the grave bed. As I recall, they will absorb ammonia and are supposed to be in a bag and removed after a period of time for rinse/soaking to remove that collected ammonia. If they are left in gravel bed, I expect they are holding ammonia and may be leaching out the ammonia they originally absorbed. I may be wrong but Cory would be able to verify any of that info.