Chemical Filtration
Fundamental to the success of a healthy aquarium is theConsequently, all carbons leach phosphates into water.

stable aquarium environment made possible by scheduled

Some carbons (coconut) appear to leach less phosphates,

water changes and filtration. Water changes provide

but only because they are microporous. Such carbons

systematic removal of wastes not normally removed byfunction better as gas phase filtrants and are not suited for

filtration and restoration of a balanced ionic environment.

water filtration. Carbon cylindrical pellets are engineeredNo system exists, despite irresponsible or misinformed

for use in air filters and are not a good choice for waterclaims to the contrary, that can replace water changes.

filtration.

Carbon. The most familiar chemical adsorbent is activatedSeachem’s Renew™ is an excellent economical replacement

carbon. Despite the appearance of many new synthetic

for granular macroporous activated carbon. It has anadsorbents on the market, carbon still remains an excellent

equivalent capacity for organic removal as many carbons; itfilter material. Unfortunately, not all carbons are equal anddoes not release phosphates; and, being white, it darkens

an enormous amount of misinformation exists. Activatedwith use, indicating exhaustion. It has a total surface areacarbon for the aquarium should be a little larger than pin-ranging from 500 to 600 m2/cc and a pore volume ranging

head in size (granular). When washed and dry, it should befrom 0.5 to 0.6 mL/cc with an equivalent molasses number

dull and not shiny. It should also tend to float atof 600 to 700. In addition to sharing somefirst. Good activated carbon should feel

adsorbtive properties of carbon, it has

hard and not crumble, but will

ion-exchange properties that provide

fracture under finger pressure. The

it with a capacity to remove ammonia

best carbons are usually produced

from freshwater that exceeds that offrom bituminous coal and have a highzeolites. It has a limited, butporosity and low density. Look for high total
surface area (450–550 m2/cc) combined with a high pore

demonstrated capacity to remove nitrites,nitrates, and phosphates.

volume (0.45–0.60 mL/cc) or high molasses number(500–700), indicating a porosity suitable for water

Other types of chemical filtration include synthetic

filtration. A high iodine number indicates microporosity

adsorbents, ion exchangers, insoluble oxides, and zeolite.

suitable for gas filtration. Look for a carbon with low ash

Zeolites are white, dusty clays, usually sold for removing

content, reflected by little or no effect on the pH of pureammonia from freshwater. It has come in vogue to promotewater. Seachem’s MatrixCarbon™ is unique in that it

certain zeolites for the removal of nitrates in sea water byincorporates these features into a spherical pellet, whichmolecular filtration. Neither the kinetics of ion exchange

has ideal hydrodynamic properties.

nor that of molecular sieving by zeolites offer a practicalmeans of removing nitrates from sea water to any useful

All activated carbons are produced from materials that wereextent. The only practical means of removing nitrate fromonce living, be it coconut shell, wood, or coal, and all living

sea water remains water changes or the biological approachmaterials are rich in phosphates for the simple reason thatof algae or anaerobic filtration. Seachem’s denitrate™ andphosphates are essential to all earthly life forms. In fact,

Matrix™ serve as both aerobic and anaerobic support

phosphates are the very backbone of DNA, the genetic

materials.

material for life itself. The activation of carbons by heating
to over 900 F in the absence of air does not destroy

Synthetic ion exchangers are useful in freshwater to help

phosphates, but converts it to soluble orthophosphates.

control ionic balance, remove ammonia, nitrite, and nitrate.

1000 Seachem Drive • Madison, GA 30650 • 706.343.6060 • FAX 706.343.6070 • 888-SEACHEM • www.seachem.com

In marine water, some ion exchangers can remove limited

synthetic adsorbent that retains all of HyperSorb's™

nitrite and nitrate, but have no significant effect on

qualities along with the added advantage of possessing aammonia. But, generally, the most useful function of ion

four fold greater capacity (than HyperSorb™) with virtually

exchangers, in both fresh and marine water, is organic

no impact on trace elements.

removal, and in this they excel. Although not an ion
exchange process, the ability of certain ion exchangers toCupriSorb™ is a narrow spectrum, synthetic adsorbent

remove organics can be phenomenal in both marine andbased filter material for removing copper and heavy metals

fresh water alike. The ability of ion exchangers to remove

from either freshwater or marine water. It extracts all types

organics is related to their hydrophilic and hydrophobicof copper, including chelated copper, and remains effective

matrix structure and porosity, much the same as uncharged

until it turns a deep blue-black color. It may be regenerated

polymeric adsorbents. Synthetic adsorbents and ion

repeatedly. If placed in continuous service, it will gradually

exchangers with porosity suited for organic removal are

extract even precipitated copper and make invertebrate

macroporous and have low cross-linkage, giving them aculture possible in tanks previously heavily treated withlightly colored appearance. Darkly colored resins tend to becopper. CupriSorb™ is a powerful copper specific chelating

microporous and highly cross-linked and are not well suited

resin. Competing products are not chelating products, butfor organic removal.

merely cation exchange resins. Such resins can remove
copper from freshwater but are ineffective in seawater.

Insoluble oxides are either aluminum oxide or iron oxide
and these materials are used for removing phosphate fromwater. They function best in seawater and at high pH.
Spherical beads, rather than granules, of these materials arehydrodynamically superior and thus function best.
Seachem’s version of this product is PhosGuard™, aspherical porous bead of aluminum oxide that has a very
high capacity for both phosphate and silicate.
SeaGel™ is formulated from MatrixCarbon™ andPhosGuard™, and is optimized specifically for aquaria
where organic color body and acid removal is required
without the introduction of phosphate. It is particularly
effective in correcting algae problems in both marine andfreshwater aquaria. It is not recommended for phosphatebuffered freshwater aquaria.
Seachem's HyperSorb™ is a premium synthetic adsorbent
with outstanding organic removal capacity and ionicmanagement abilities. It is ideal for all types of water,
including marine, brackish, and a broad spectrum offreshwater from acid to alkaline. It has all the advantages ofcarbon and none of the disadvantages. HyperSorb™
changes color progressively as it becomes exhausted, andthen can be easily regenerated with ordinary household
chemicals. Regeneration is near 100% effective and can beperformed repeatedly. Purigen™ is a premium grade