I have a Rubbermaid trash can with a lid that I use just for mixing water. I have a 500gph power head in there that continuously mixes the water, it also pumps water back to my sump. Along the side of my backyard, I have a "dedicated hose" to do water changes, it runs to the back of my yard and stays there always. In my tank, there is a hose with a tee that has a ball valve on it. Now when I do a water change, I connect another "drain hose" from the "tee" to the "dedicated hose". I then open the ball valve and drain out whatever amout of water, usually 15-20 gallons. When finished draining, I disconnect the drain hose from the dedicated hose and connect it to the powerhead in the trash can and then pump the new water back into my sump. It sounds complicated but its not and its a lot easier than carrying 5 gallon buckets back and forth.