There are many ways to prevent your water feature from algae and general dirt. First of all the more obvious way would be to empty your feature and give it a good clean when you start to notice a colour change in the water.
Another way is to check in the reservoir of your feature to check that no leaves or anything else from your garden has got into the feature. This could affect the performance of the pump if there is anything blocking it. It may be useful to give your pump a wash in warm soapy water to ensure that it is kept clean.
At UK Water Features we find that Banish or Fountain fresh are both a great product to keep algae away. Both of these products are pet and wildlife friendly. The products are recommended to be used every two weeks from May to September and every four weeks at other times in the year.
The bottles both come with a measuring unit to make the amount easy to read. 25ml is the recommended amount. Once the feature cleaner has been used you just need to simply remove any dead algae if it is left behind. This will also prevent any smells from your feature and make it easy to look after your water feature.