The Penn Plax Aqua Mist Air Stone is a green colored aerator for your fish tank. It produces lots of bubbles, and a better oxygen supply for your fish, allowing them to breathe better. It can be buried under the gravel, thereby giving your aquarium a cleaner look. Shop Penn Plax for all your pet needs. Penn Plax sells fish, reptile, bird, small animal, cat, and dog items. Fish items include stunning tanks, breeding tanks, ornaments, and décor, as well as air pumps, vacation feeders, bubble walls, nets, dividers, thermometers, gravel vacuums, algae scrapers, air tubing, toxin removers, air stones, filters, and cartridges. Small animal items include habitats, wheels, tubing, feeding dishes, and toys. For birds, Penn Plax sells perches, toys, cuttlebone, and swings. For dogs and cats, there are available toys, stairs, crates, furniture, and cooling collars and mats. Reptile items include terrariums, lamps, climber vines, rocks, and other décor. Penn Plax is your one stop shop for everything you need, pet wise.