I have a deep acrylic tank (36") with 3 sides that need to be cleaned. Coralline algae is growing like crazy. I have been using a kent scraper, but the blade gets dull very quickly. (I do sharpen it using a grinder - but they still don't last very long) My magnavore VIII does not touch it. My main problem is the thick plates of algae that form near the bottem where I don't have a very good angle of attack with my scraper, and in the corners. Anybody got any good ideas? Are there any soft metal scrapers (aluminum) out there which will not scratch the acrylic?