What can I use to clean a water trough?

How to clean your water tank
  1. Empty the tank.
  2. Scrub it clean.
  3. Rinse the tank with a 10 percent bleach solution (1 part bleach to 9 parts water).
  4. Rinse it twice more with clean water.
  5. Refill the tank. The horses can safely drink from it right away.