I'm not so sure that an aerator will solve your algae problems. Although overall a bottom aerator has proven to more helpful in reducing filamentous algae (FA) than a fountain. I have never heard from a pondowner that found that a fountain aerator helped very much long term (2-3yrs) to reduce algae. See this thread:
http://www.pondboss.com/ubb/ultimatebb.php?ubb=get_topic;f=14;t=000324. This person has two bottom aerators (1 windmill, & 1 1/3hp compressor) with a total of 3 diffusers and he still has FA problems. If a pond has dissolved nutrients in the water column, it has never been proven with published reasearch that an aerator can remove the dissolved nutrients that are feeding the algae. I have seen lots of FA in ponds with all sorts of aerators.
The dissolved nutrients that I am primarily referring to typically enter a pond from runoff from the watershed. A bottom aerator can in many cases help suppress SOME nutrient release from the recycling from the deep bottom anoxic (oxygen deficient) sediments. Bottom line if there is a choice between a fountain and bottom aerator; choose bottom aerator. The success of the aerator at reducing the FA is dependent on the source of the nutrients that are feeding the algae.
