42 Phosphate-silicate adsorber

Iron-based phosphate adsorbers can also remove silicate from the water at the same time. The absorption capacity depends on the water conditions (pH, temperature, salinity) and on the material used. 

Simple granular adsorbers are inexpensive, but have a high dust content. If the dust is removed beforehand by washing the adsorber, a proportion of the capacity is lost. Also, significant amounts of iron can be released during the start-up period - the brown coloration of the water is not desired by everyone. The iron release also leads to iron fertilization, which can trigger an algae bloom, for example. Simple granulate types cannot be used in fluidized bed operation. The granules would be pulverized. 

High-performance adsorbers are more expensive, but are characterized by several advantages: the color release (iron release) is considerably lower, the dust content tends to zero, and the material can be operated in a fluidized bed filter or, better, in a fluidized bed reactor. 

A performance comparison of different adsorbers is only possible in direct tests. Statements such as "1 liter removes so-and-so much phosphate" say nothing without further specification. If the desired final concentration is not specified, such statements are useless. The capacity in g/liter increases with the final concentration in the aquarium water. Only so-called adsorption isotherms are meaningful: