Chemical
filtration is just what is sounds like. It is the use of chemically
enhanced products to remove those things that ail you; copper, dissolved
organics, nitrate/nitrite/ammonia, phosphates, etc. Beware of fantastical
claims of effectiveness. Most of the claims are just claims.
However,
there is one tried and true chemical filtration medium: activated carbon.
Activated carbon helps remove dissolved organics from the water. Over
time, as an aquarium matures, dissolved organics build up in a closed
system. This causes the water to take on a yellow tinge. Activated carbon
is great for removing this. Beware though, that is not all it removes.
Activated carbon is reported to deplete some beneficial trace elements
in the water. Therefore, a lot of people have taken some different approaches
to using carbon other than full-time in a canister filter.
If you choose
to run a sump with your system, this is a good place to
drop a filter bag of carbon. The water is allowed to flow around the
carbon, reducing the amount of trace element striping that is done,
but still removing the yellowing compounds from the water. If you don't
have a sump you can drop the same filter bag behind the rockwork in
the display tank and accomplish the same thing. Some protein skimmers,
particularly the CPR BackPak, have a media chamber where you can drop
the filter bag in and affect the same thing.
Another issue
to be careful of with activated carbon is the leaching of phosphates
into the water. High phosphate levels encourage unwanted algae growth,
which indirectly increases maintenance tasks. When you choose an activated
carbon, make sure it specifically states that it does not leach phosphates.
Summarizing
the basic filtration choices, biological filtration is mandatory, although
live rock and live sand are not a requirement (just a dang good idea).
Mechanical filtration is not mandatory, as some of the removal of particulate
matter will occur during water changes. Protein skimming, however, should
be considered a must for maintaining good water quality. Chemical filtration
is completely optional, and should only be used until a specific problem
is resolved, with the exception of activated carbon. Phosphate-free
activated carbon can be used full-time, part-time, or not at all. Your
call.
The end goal
of all types of filtration is superior water quality. This is the main
thing that will effect the health of all of your livestock.