Article: Regular cleaning can remove existing algae from your birdbath and prevent the build up of new algae. To clean your bird bath, start by removing all the water and discarding it. You will need to replace it with new water when you're done. You will need a small scrub brush to clean out your bird bath. In most cases, it is unnecessary to use cleaner. However, if your birdbath is very soiled or dirty, use a mild detergent. Clean the bottom of the bird bath and the sides, scrubbing off any dirt, debris, or visible algae. It's best to use a hose to rinse off your birdbath, especially if you used detergent. Hose down the inside of your bird bath until all soap residue is gone. It is very important to be thorough about rinsing a bird bath. Birds are very vulnerable to detergents and it can be harmful for birds if there's detergent left in the bird bath. Once you're done, you can refill your birdbath.  Use fresh, clean water to refill the bath.

What is a summary?
Remove the existing water. Clean the birdbath with a small scrub brush. Rinse your bird bath. Refill the bird bath with fresh water.