Reef Aquarium Filters - Chemical Filtration Explained
Reef Aquarium Chemical Filtration Overview
Chemical filtration is defined as using any medium that alters the composition of the substance it is placed in. This means that when a chemical filtration medium is placed into an aquarium, it changes the composition of the water by removing dissolved organics, toxic metals, chloramines, enzymes and gasses. There are many types of chemical filtration medium used in marine and reef aquariums. The most widely used media are listed and explained below for easy reference.
Activated Carbon For Reef Aquarium Filtration:
By far,
the most common method of chemical filtration in the marine
and reef aquariums is the use of activated carbon. Activated
carbon is manufactured by exposing coal carbon to high heat
and steam which creates a micro-porous material. Microscopic
pores absorb heavy metals and organic molecules by trapping
the molecules through a process know as molecular sieving.
The highest quality activated carbon is made from coconut
shell and is the type recommended for reef aquariums. The
best activated carbon will be low in ash and will float and
fizz when initially exposed to water.
In recent years there has been a large amount of discussion
on the possibility of activated carbon leaching dangerous
levels of phosphate into reef and marine aquariums. Indeed,
activated carbon does leach phosphate as it is being used in
an aquarium, but not at dangerous levels. Activated carbon
leaches a non-toxic amount of phosphate because it is made
from coal which was once plant matter, and plant matter
contains a high level of phosphate.
It's important that you only purchase high
quality activated carbon that has been acid washed prior to
packaging in order to reduce the amount of ash on the carbon.
It has been found that activated carbon with higher ash
content leaches more phosphate into the water than those with
a low ash content. Yes, this means you should use the
expensive carbon (relatively speaking).
It has also been said that activated carbon removes trace
elements needed by corals in reef aquariums. Yes, activated
carbon will remove an amount of trace elements from the
aquarium water, but in essence, that’s its job (to
remove dissolved elements from the water). The amounts of
trace elements that are removed are easily replaced by using
a supplement like Kent Marine Trace Elements. The pros of
removing the dissolved organics and heavy metals far outweigh
the cons of losing trace elements that can easily be
replaced. We recommend using activated carbon to maintain a
clean, odorless and colorless aquarium while dosing it with a
high quality trace element supplement to replenish those lost
by using the carbon.
The amount of activated carbon to use varies with the use of
the aquarium, but as a general starting point we recommend
about ? cup for each 20 gallons of water, replaced every 6
weeks. You must make sure to thoroughly wash the carbon
before use in order to remove as much ash as possible. When
washing, place the carbon in a filter bag and rinse until the
water running off of the bag is clear. If you massage the
carbon you will create more ash, so just rinse without
disturbing the particles and use when the water runs
clear.
Phosphate Removers For Reef Aquarium Filtration:
Phosphate
removers include Aluminum and Iron Oxide granules. It has been
found that Aluminum Oxide will leach aluminum into the aquarium
and has since been phased out with the advance of Iron Oxide.
Iron oxide is a mineral that has the property of absorbing
phosphate and other materials into its porous structure by
means of ion attachment. This type of chemical filtration is
best used when water is flowing through the medium at a slow
rate, so a phosphate reactor is often used.
A phosphate reactor is just a canister that houses the
phosphate removal medium and allows it to tumble as a power
head slowly circulates water through it. There are many
different manufacturers of phosphate removal medium and each
medium should be used per the manufacturer’s directions.
Such removers are very useful materials in the reef aquarium,
and when a developed reef has been established, it is almost
mandatory to use some sort of phosphate remover. The levels of
phosphate in the reef aquarium should always be kept below .7
ppm, but if you are planning on having small polyp stonies
(SPS’s) in your aquarium, levels below .3 ppm are
mandatory and levels of 0 ppm are ideal.
Nitrate Removers For Reef Aquarium Filtration:
Nitrate
removers are very porous material that resemble crushed coral
or gravel and work by increasing the levels of natural
anaerobic de-nitrification in the aquarium. These products
accomplish this task by being impregnated with anaerobic
bacteria that naturally dissolve nitrate.
The same thing that is accomplished while using a nitrate
remover happens constantly when a reef has an incorporated
Refugium (which we’ll be discussing later). Anaerobic
de-nitrification occurs best when exposed to low levels of
oxygen; this is why refugiums have a deep sand bed. Thus,
nitrate removal mediums should be positioned in an area with
low flow rates. Levels of nitrate should never exceed 10-15
ppm, but ideally, a level of below 5 ppm should be
maintained.
Poly Filters For Reef Aquarium Filtration:
Poly
filters are sponges, cloths or other materials that have been
impregnated with one of the materials previously listed
(activated carbon, iron oxide, etc.) or another chemical
material. The main selling point for this type of filter is
convenience. They are often marketed as “cut to fit your
filter” or “only use as much as you need.”
These filters are actually just sponges laced with the
by-product (dust) of one or more of the manufactured materials
above – a phosphate removal poly filter is a sponge with
Iron Oxide dust impregnated into it; a carbon poly filter is a
sponge with carbon dust impregnated in it, and so on.
These types of filters are not recommended by
ReefAquariumInfo.com as you can never know exactly how much
active product you are using, and you will always spend more
money on this type of filter due to the additional
manufacturing processes needed to create it.
