Fluidized Reactors
Fluidized reactors have become very popular in the
last few years for reefkeeping. Historically fluidized reactors were used
for biological filtration and typically filled with sand or some other
inert media to promote the growth of beneficial bacteria to aid in the
reduction of Ammonia to Nitrate via the Nitrogen fixation cycle.
The fluidization of the media greatly increases the surface area of the
media allowing for a greatly increased amount of these strains of organisms.
In the reef aquarium however fluidized reactors are being used for chemical
filtration instead of biological filtration.
Fluidization of media is a very simple and effective method to increase
the surface area of a given substrate to increase the transfer rate between
the liquid and solid phases. Typically the substrate is fluidized using
a controlled velocity of fluid to convert the substrate from a solid state
to a liquid like state. Fluidized beds have many advantages including
high transfer rates when used for chemical filtration as well as huge
surface areas when in use as a biological filter.
Fluidized reactors used for chemical filtration in reef tanks typically
contain phosphate adsorbing media, either granular ferric
oxide (GFO) or alumina oxide (AO). GFO is typically used however due to
some risk of releasing aluminum back into the aquarium water when using
AO based media. GFO based adsorbents such as Rowaphos
or Phosban are very popular as they will remove both
organic and inorganic phosphate from the aquaria at a very rapid rate.
Some care must be taken to reduce phosphate levels at a slow controlled
rate or rapid tissue necrosis (RTN) can occur. However if low phosphate
levels are achieved in a reef aquarium it will help reduce nuisance algae,
increase coral health, color, growth and improve the reef bioload. It
is a goal in maintaining a reef tank to keep nutrient levels such as phosphates
at or close to zero (0-undetectable).
Granular activated carbon (GAC) is widely used in fluidized
reactors as well as Purigen which is a synthetic adsorbent
which has similar affinities toward organics comparable to GAC. Purigen
will not adsorb trace elements or other metals such as carbon does which
may be a benefit when the goal is to reduce Nitrates in a reef tank.
Overall fluidized reactors can play an important role in the reef aquarium.
Not necessarily by providing biological filtration but as a means to export
unwanted chemical elements from the captive reef by the use of the different
types of media available to the reef keeper
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