Aqueon Siphon Vacuums (A.K.A. gravel vacs) are a great way to keep your tank clean and your aquatic friends happy. These gravel vacs have a self priming valve, that allows you to start the water flow using an up and down motion (instead of mouth starting your siphon... gross). Assorted sizes ensure that you don't get a vac that is too big or too small. Each of these gravel vacs comes with a six foot hose.
Note: Mini vacs are 1 inch in diameter, Medium vacs are 1.5 inches in diameter, and Large vacs are 2 inches in diameter.
Rivers to Reef says: We always recommend doing at least a 25% water change every two weeks. The way you stock and filter your tank can increase or decrease the frequency of water changes. Tanks with high bio-loads, like those with heavy eaters (such as Cichlids and large Catfish), Goldfish (who produce tons of ammonia), and aquatic Turtles should consider doing at least a weekly 30-50% change once your tank is established.
In most cases you should never perform a 100% water change on your tank!