Aquaristics / garden ponds

Filter material for the removal of phosphate and silicate from marine and freshwater aquariums and garden ponds


Phosphates together with nitrates are the main nutrients for algae. Therefore excessive phosphate concentrations promote unwanted growth of algae in fresh and saltwater aquariums. The algae often occur as single-celled organisms floating freely in water, leading to a clearly perceptible green color of the water. In addition algae form green or brown deposits on the panels of the aquarium or occur in the form of thread or brush algae growth on water plants. Principal origin of phosphates in aquarium water is the fish feed. However tap water used for filling the aquarium also often contains phosphate in concentrations which may facilitate an increased growth of algae.


FerroSorp® Plus is a high-performance adsorption granulate based on iron hydroxide. It was developed specifically for the adsorptive removal of phosphate and silicate from waters from fresh- and saltwater aquariums and garden ponds. The filter medium is due to its large surface area of about 270 m2/g capable of binding phosphate ions rapidly, effectively, and irreversible. FerroSorp® Plus is offered in different grain sizes and thus permits the use in special filter cartridges, which operate on the principle of a floating bed filter or in filter bags, which can be used in virtually any multi-layer filter. Besides phosphates and silicates harmful heavy metal ions such as lead, copper and zinc are bound by FerroSorp® Plus too.

Furthermore, a fixation of dissolved organic water pollutants by adsorption is possible. Following equation shows the conversion of iron hydroxide with phosphate ions simplified:



The binding capacity of FerroSorp® Plus for phosphate depends on various parameters, such as grain size used, phosphorus concentration, presence of competing ions (silicate) and operating conditions in the filter. Experience shows that loading rates of 5 – 15 g phosphorus per kg FerroSorp® Plus can be achieved . Under normal feeding conditions in a 200 liter aquarium that is filled with 1 cm fish per liter an amount of 400 g FerroSorp® Plus should be be changed approximately every 6 months. The phosphorus concentration in the water should be checked regularly using a commercial test kit. If a rebound in concentration of phosphate is detected, the filter media should be replaced. Spent filter granulate can be used as plant fertilizer or disposed of with household waste.




Advantages at a glance

  • High cleaning performance at low cost
  • High loading rates due to a highly porous surface
  • Applicable in different filter systems