Hi everyone ! I have this terrible algae problem that is a real PITA ! I can't seem to get my silica levels in my tank below 0.5ppm however my Phosphate level is low at 0.02ppm (good news) I have been using a phosphate sponge in my external filter for the past 3-4 weeks with not drop in the silica levels. Futhermore, I have been using the tap water filter - I think it is a DI filter for all water changes. One thing that struck me as odd is that even with a new filter installed, the silica tests I did on the water off the new filter is still at 1.0ppm. Is this normal ??? All the tank inhabitants seem fine, it is just the algae growth, especially on the back glass, sand and on top of the live rocks are a nuisance to clean every week. Here are other info on my tank... Nitrate 0 Nitrite 0 Ammonia 0 PH 8.6 SG 1.024 Temp 79F Water Changes about 10% every 2 weeks. Thanks to anyone with any ideas on how to control this !!