Phosphorus is the nutrient in shortest supply and, therefore, the focus of a pond owner's control. When phosphorus enters a pond via your watershed, yard clippings or decomposing plants and animals, it is re-suspended in the water column and made available for pond moss, or algae, to consume. Filamentous algae is also known as pond moss because of its buoyant nature. This type of algae is a common problem in ponds, but there are several ways to prevent it from taking over.
Wield your large dip net and scoop out the mats of floating algae onto the shoreline. Since the algae is actually growing up from the bottom of the pond, reach as far underwater as your handle will allow. Rake the discarded algae and dispose of it away from your pond in a waste bin. This is the most permanent form of algae control since you physically remove the phosphorus from the pond totally preventing it from re-suspending nutrients.
Add pond dye to the water column. This is the simplest and cheapest method of algae prevention. Dyes come in blue, blue/black and black, are non-toxic to all aquatic organisms and provide a filter to sunlight entering the pond, preventing algae from using sunlight to convert carbon dioxide into organic fuel.
If copper-sensitive fish like carp, trout, koi or goldfish live in your pond, mix a non-copper based algaecide/water solution in your hand or backpack sprayer per the label rate listed on the side of bottle. If the aforementioned fish are not present, you can use the more conventional and effective copper-based herbicide. Use a fan spray tip and lightly mist the floating mats of algae to ensure an even distribution of chemical.
Install a bottom-based aeration system. Mount your compressor inside a ventilated, weatherproof enclosure on the shoreline or wherever power is available. Connect one free end of weighted tubing to the compressor; connect the other end to your diffuser's hose barb, making sure to use a stainless-steel clamp to secure the connection. Maneuver your boat out to the deepest area of the pond and slowly lower the diffuser to the bottom, making certain it rests right side up. Bottom based aeration creates an oxygen rich environment at the sediment-water interface which binds up phosphorus with naturally occurring iron. This effectively renders it unavailable for algae to use as a food source.