We have had a pool in Roatan Honduras for around the last seven years. We have been using Baquacil, and its algaecide/sanitizer has worked well for us. We never had algae, while the chlorine pools were using lots of many different algaecides frequently, and often without effect. The tropics are a real testing ground for algae. Baquacil's advantage is reportedly that it does not break down as readily in sunlight. Its oxidizer, hydrogen peroxide, also works well, except both chemicals need to be shipped here, and the oxidizer must be shipped as a hazardous substance, which involves extra expense. I came to this site when bumping into an ad for potassium monopersulfate, which looks like it would do a similar job for a much lower price.