To fill the tank back up you adjust your sinks water temperature as needed, close the sink drain (so it will continuously fill with water), and leave the water running (traditional sinks usually don't overflow as they have a top drain hole). Place the end of the hose into the aquarium and then plug in the pump by the sink and place the pump into the sink of continuously running water.
Once the tank is filled with clean water unplug the pond pump (assuming it doesn't have an off/on switch like mine), place your finger over the end of the tube in the tank and bring it to sink to drain out any excess water in the tube.
I use the Tetra 140GPH Pond Pump, it comes with 3 different sized hose adapters (a 1/4, 3/8, and 1/2 inch ID) and has an adjustable flow rate (which gives off around 3 inches of head at its lowest setting and over a foot of head on its highest setting). Keep in mind the GPH when looking for a pond pump because that will control how fast you can get your water change/s done (with the 20ft vinyl hose I attach to this pump I can basically empty 1 gallon of water per minute).