Bird baths generally get dirty from seed and water which sits too long.  So, start a regular weekly cycle of cleaning your bird feeder and make sure to use a brush to clean anything that may be just starting to grow.  A solution of one part bleach to 10 parts water will more than enough bleach to kill anything growing.  There are also cleaning products and additives available to help keep your bath cleaner for a longer period, and will not harm your feathered friends.  You can also add a fountain to your bird bath, which will keep moving the water and even filter it, to keep your bird bath cleaner, longer.

Another option is purchasing a bird bath with a removable plastic bowl, available at Barn in the Sticks, and manufactured in the United States by Looker Products.  It is available in two sizes and with a variety of different bases, including hanging and standing models, and even a heated model!

Remember that birds need water, a key to attracting birds and a larger variety of birds is having water available for them, whether it is a nearby lake, river, or your own beautiful bird bath.