Vacation Block 20g is suitable for all freshwater aquariums and ponds. The Vacation Block when placed in your aquarium will slowly dissolve, releasing small particles of food and help stabilise pH. One 20g block will feed 10-15 average sized fish (3-4cm) for approximately 3 weeks. For best results place block near an air stone or filter outlet to aid dispersion of food as block dissolves. Remove remainder of block when you return. For healthy fish, change aquarium water regularly and maintain water temperature of 22-27C with a pH value of 6.8-7.2.