Ammonium chloride in an easy to use dropper bottle for fishless cycling. Add 4 drops of solution per gallon of water for an ammonia-nitrogen concentration of 2 ppm (2 mg/L). When cycling do not let the ammonia nor nitrite get above 5 pmm as nitrogen. Monitor cycling progress with ammonia, nitrite and pH test kits. Never add to aquaria that contain fish, invertebrates or corals.