Once your tank is up an running and stabilized make sure to check your ph levels. They can and will drop with time. This is cause when the ammonia is broken down and the hydrogen ions are released into the water. To solve this depending on the ph you can change it slowly by adding 1/8 tbsp of baking soda. Caution the ph drops slowly so raise it slowly!!!

Keep your ph around 7 - 7.5 anything below that is acidic.