Please tell us about your water system (pond, lake, pool, tank, process, etc.).
Location will help us if it can be seen from Google Earth so that sizing and a layout can be done.
Else let us know the length, width, depth information so we can size the proper unit for you.
Describe the algae in your system (scum, filamentous, mats, green water, etc.).
Do you have aeration? Is the pond spring fed?