Oase OptiMax Aquarium Pumps are small, yet powerful pumps for water movement, and circulation. The complete line, consisting of Optimax 300, 500, 800, 1000, 2000, 3000, 4000 & 500 Pumps are perfect for ater circulation, or as return pumps to the Aquarium. (ie. Sump Pumps)Key Features: Can be used in Freshwater or Saltwater applications. Adjustable water flow on all models. The 6 larger models can be dry installed. Very Quiet & Economical.