Filamentous algae are unicellular organisms that intertwine and form long, slimy chains or filaments.
Its filaments multiply incessantly and cling on the pond and rock surfaces, giving an awful look and putrid smell on your much-loved water features.
Much worse, the filaments can create thick and large mats that appear the same as wool.
Filamentous algae are silent and quick killers that attack the bottom of the water and attach to rocks, aquatic plants, and pond's surface.
They float on the surface of the pond and cause unsightly mats or known as "pond scums" that present numerous problems on the ponds.
Filamentous algae are threat to the life of aquatic animals and the pond itself.
The excessive population of filamentous algae of can deplete the oxygen exchange and trigger massive fish kills.
Given proper preventative treatment, the increase of filamentous algae population can still be controlled, or removed.
There are different control methods used namely: mechanical/physical, biological and chemical.
Mechanical/Physical The piles of filaments can be raked from the bottom of the pond.
Another way is the fertilization of "phytoplanktons" to hamper the formation of filamentous algae.
Using non-toxic dyes or colorants on the pond can block off the sunlight from penetrating the water.
However, these colorants can also affect the natural food chain of the pond.
Biological There are several species of fish that help prevent the growth of filamentous algae.
One of this is the grass carp.
Grass carp stocking is practiced in several fisheries in United States, because grass carp is deemed to consume filamentous algae for food.
However, grass carp consumes first all the vegetation submerged in the water before it finally eat the filamentous algae.
Otherwise, grass carp stocking can control about 10 to 20 per surface acre.
Tilapia is also used for control, but this specie cannot survive low temperatures below 55° F.
It is not advisable to stock tilapia before April or May because it will die in November or December.
The recommended stocking rates should be 15 to 20 pounds of male and female Mozambique tilapias (Oreochromis mossambicus) per surface area.
However, tilapias are not reliable for vegetation control especially if the pond has severe algae problem.
Meanwhile, several states require permit from a certified wildlife department before you can stock tilapia and grass carp.
Chemical The chemical ingredients known for treating filamentous algae are copper, sodium carbonate peroxyhydrate, and diquat.
Copper compound is used as herbicide for the removal of filamentous algae.
All copper compounds can be toxic to the pond, so it is important to take proper precautions before using this treatment.
You must test the pond water's alkalinity first and adjust the volume of copper treatments based on the water's alkalinity level.
The sodium carbonate peroxyhydrate based herbicide is used for the control of blue-green algae.
However, this chemical is not effective in treating macroalgae like Chara or Nitella and other higher plants.
Diquat is a contact herbicide that controls several species of filamentous algae.
It is applied by pouring the chemical directly into the pond or by diluting the concentrate with water below the water surface.