If you have brown algae or green algae, I recommend turbo snails. I had some severe algae blooms when my phosphate levels accumulated, but after adding three turbo snails, I haven't seen the algae since. They go at it like lawnmowers, and they get everywhere! They have even managed to get the filter water intake clean...I don't know how, but they did.
What type of water are you using for your water changes? If you are using city tap water, then that is part of the problem. It conatins high levels of phosphates which can cause algae blooms. Try using reverse osmosis water, available from most any LFS for about $.49 a gallon. Also, if you are washing tank decorations in your dishwasher, then that can be a big problem, as dishwater detergent can contain huge amounts of phosphates.
Oh, and is your tank in direct sunlight during the day?