I bought two of the Reliance Hydroller water containers from campmor.com. Hydroller 8G/30L | Water Containers & Accessories | Reliance Products. Each holds 8 gallons. They are designed for camping, but work perfect for water changes. They have a wide mouth and easily hold powerheads. I mixed up 8 gallons of saltwater in one and used the other to drain 8 gallons from the tank before putting the powerhead with tubing into the new saltwater and into the tank. I did the water change in under 15 minutes. The containers are heavy plastic, safe for drinking water, thus safe for aquarium use. They are wheeled and have a handle. The container holding the old water is easily rolled to the sink for disposable using the powerhead and tubing. Since my DH hates my tanks, I must do all maintenance on them myself and this makes it so much easier. Not quite as easy as the 3 gal that I use a turkey baster to do water changes, but almost.