you could go to a fish store and look for a magnet scraper that can help you remove algae off the sides of your tank, if its algae on ornaments and such, you could consider an "algae eater" as others have mentioned, but algae eater is a broad term used to refer to several popular species of algae eating fish.
One popular species is the pleco, but plecos get large - some grow to 2 feet in length.
The Chinese algae eater is a popular fish and does not grow as large as the pleco and very effective in reduing algae in tanks.
The otto is a very popular algae eating fish but they prefer to be kept in groups, so a larger tank is required. They usually need to be kept in groups of 4 or more.
The corydoras are also effective in algae control and removal but they also need to be kept in groups of 5 or more.
In my personal opinion, the chinese algae eater is one of the most effective in controlling the algae, and because of its relatively small size, it can be accomadated in most aquariums. However, all the fish mentioned above should be kept in tanks no smaller than 10 gallons depending on the number of existing fish that you already have. All the fish mentioned also require heaters, except maybe the pleco.
Another effective way in controlling algae growth is to introduce live plants into the aquarium, algae grows when there are excessive nutrients in the tank, and having live plants will fix this problem. The plants will feed off the nutrients while at the same time provide a great looking tank and hiding places for fish. Some easy to care for plants that i can reccommend are the java fern, java moss and the banana plant.