EasyStart is safe. A product containing live nitrogen bacteria that can be used as an aid in maturing the aquarium. With the substance, you get a fast-acting bacterial strain. It removes impurities that come with tap water.
Dosage: when starting the aquarium, shake the bottle vigorously and add 10ml per 50 liters of water day 1, day 7, day 14. 100ml is enough for 165 liters when dosing as above three times. If nitrite problems occur, increase each day until the nitrite is gone. The turbidity of the water disappears after a couple of hours. Also works in salt water.