Dymax AP air pump series is designed with advanced air-compressing system and a multi-level muffler that provides extremely low noise. This pump is ideal for action ornaments, bubbling air stones for oxygenation, sponge filters, corner filters, under gravel filters, creating current to prevent stagnant water, as well as protein skimmer for marine. Available in 4 models: AP100 has one outlet with built in pressure control operating at 2W. AP300 has one outlet operating at 2.5W. AP500 has two outlets operating at 2.9W. AP700 has two outlets with built in pressure control operating at 2.9W.