* Optical grade magnifying lens with 3" viewing portal is perfect for aquarium photography with focal range approximately 2 to 6 inches. * Held in place by strong rare earth magnets for use on tanks up to 3/8" (10mm) tank wall thickness * Easily moves around the tank for viewing from any location * Great at checking for any early signs of disease or pests on your reef coral or fish! * Designed for Nano size tanks * Deep See is Safe for both glass and acrylic aquariums!