A system 10 for mixing a fluid in a tank 12 includes a mixer assembly 14, a housing 28, and an actuator 34. The mixer assembly 14 has a motor 30, a shaft 24, and an impeller 22. The housing 28 is disposed in a side wall 18 of the tank 12. The housing 28 has sufficient volume to contain the impeller 22. The actuator 34 is configured to retract the mixer assembly 14 and draw the impeller 22 into the housing 28. The mixer assembly 14 has a first conformation and a second conformation. In the first conformation the impeller 22 is disposed in a main portion of the tank 12 and configured to mix the fluid in response to rotation of the impeller 22 via the motor 30 and shaft 24. In the second conformation the impeller 22 is disposed in the housing 28 and out of the main portion of the tank 12.