Water fountains will keep working a very long time with scheduled cleaning and maintenance. Leaves, twigs, and insects very often find their way into fountains, so it is important to keep yours free from such things. Additionally, anywhere light from the sun combines with still water, algae can develop. To avoid this, take vinegar, hydrogen peroxide, or sea salt and add straight into the water. Another option is to mix bleach into the water, but this action can sicken wild animals and so should really be avoided.
A complete cleaning every three-four months is best for garden fountains. The first task is to get rid of all the water. When it is empty, scrub inside the reservoir with a mild cleanser. If there are any small grooves, grab a toothbrush to get every spot. Be sure to carefully rinse the inside of the fountain to make sure all the soap is gone.
Some organisms and calcium deposits can get inside the pump, so it is best to take it apart and clean it thoroughly. To make it less strenuous, soak it in vinegar overnight before cleaning. Build-up can be a big hassle, so use mineral or rain water over tap water, when possible, to prevent this dilemma.
Lastly, make sure your fountain is always full by looking at it every day - this will keep it in tip-top shape. Permitting the water level to get too low can helpful hints cause damage to the pump - and you certainly don't want that!