I first used Bio Sphere two years ago and it worked wonders on my 1/2 acre, 10' average depth pond. Last year I tried a less expensive liquid that I purchased locally and my pond went downhill fast. This year I've been doubling the treatments to get the pond back in order and it's looking GREAT! This is the only product that I've used that cleared my pond quickly and reduced and then eliminated algae. Well worth the money when used properly and consistently.