It's an external canister filter for tanks up to 100 gallons in size.
Brad's Deals Editor Jim,
This Three-Stage Aquarium Pump Filter was already on sale for $49.94, but you can get it for $40.99 when you apply our exclusive code BRADSBCP1292 during checkout at Best Choice Products. Shipping is free, and that's the best price we can find anywhere by about $9. The external canister filter increases oxygen and helps you maintain a clean aquarium. It fits tanks up to 100 gallons. Sales tax is charged in some states.