INSTANT FROG is made especially for existing in ground pools up to 25,000 gallons. It drops right in the skimmer basket and lasts for six months. That makes INSTANT FROG the perfect retrofit mineral product. INSTANT FROG uses the same revolutionary mineral technology as our POOL FROG products, but requiring the low 0.5 ppm of chlorine be added by hand or with a chlorine delivery device. However, you can reduce the use of chlorine up to 50%*, which results in less eye and skin irritation, less fading to bathing suits and, best of all, less work!