As most of the above posters have said, you seem to be doing a good job with keeping it clean. Chemical cleaners are never recommended, just put some elbow grease into scrubbing, as annoying as it is. However, have you thought of using a filter or aerator to keep the water moving? Algae forms fastest in still water so even having a device to keep it moving could help. Filters will obviously keep all impurities at bay. Make sure your filter can handle larger particulates as well, food and feces may buildup and damage your it By keeping it clear of debris it should make your job a bit easier.