This article is written in response to reader questions and
suggestions. Since the publication of Reef Aquarium Filtration I and II
(Blundell 2005a, Blundell 2005b) I have received feedback from numerous
readers. While most of the comments have been of appreciation, some
have addressed terminology and concepts that had not been covered. This
article is a continuation describing some of the more philosophical
filtration practices and concepts.
First off please understand that Natural Filtration in the
purest sense only takes place in the ocean. Even then, on a coral reef
it is not sure whether or not any filtration actually takes place. Some
would view corals, fish, plankton, and algae as organisms all
contributing to the filtration of the passing water. Others would view
these organisms as part of the life cycle, all taking in food and
excreting waste, never once filtering the water and potentially
For the sake of argument let’s assume the coral reefs of the
world do have ongoing natural filtration. This filtration includes
substrate bacteria breaking down nitrogen compounds, corals eating
plankton, sponges trapping and consuming particles, and very, very
large amount of water moving through a reef system.
In the same way that one may argue of natural filtration only
taking place in the ocean; one may defend the position that all
aquarium filtration is artificial. In a manner of speaking nothing
about a captive aquarium is natural. Bioballs, protein skimmers, ozone
units, and ultraviolet sterilizers are certainly not found on a
reef….. or are they?
The Sliding Scale
It is important to notice that this article is not titled
“Natural vs. Artificial Filtration” nor is it titled “Natural or
Artificial Filtration” but instead uses the key word and.
This is not by chance but instead well thought out following the input
of fellow hobbyists. Because one could (and often do) argue that reef
aquariums do not use any natural filtration, or that they heavily use
natural filtration, we will use a sliding scale for the breakdown of
common filtration methods.
My best efforts to understand filtration methods has left me
with one overriding question. This question is what I ask myself every
time I am presented with a filtration query. The question is “In what
ways is this natural, and in what ways is this artificial?” Now you
have the question, and I encourage you to ask yourself this question
when you look at your own aquarium filtration. Some examples are
Filtration Methods Explored
For years I considered these devices to be completely
artificial and the result of some amazing human ingenuity. It wasn’t
until 1997 that I began to think otherwise. While speaking with a few
employees from a public aquarium in Portugal I began to see the natural
basis to protein skimmers. I asked a question to these employees as to
whether or not they used any mechanical/biological/natural filtration.
Their response was that the aquarium ‘only used natural filtration such
as live rock, deep sand beds, and protein skimmers’ (paraphrased).
Simply put, I was confused. I had not heard anyone previously classify
protein skimming (foam fractionation) as natural filtration. After some
follow up questions I soon understood their view. Quite near to the
aquarium these employees would walk along the Northern Atlantic
Shoreline of the Iberian Peninsula. There they could witness the
seafoam, or protein foam that was brought up on shore by the perpetual
waves. In this way, protein skimming is quite natural.
While the endless of benefits of bacteria colonized live rock
are not frequently debated what is of interest to many hobbyists are
the effects of everything else that can live on substrate. One example
of this is benefits of living sponges. One of my favorite items
available these days is the live rock produced and grown in the waters
off of the Atlantic coast of the United States. These live rock farms
in the waters around Florida produce eco-friendly rock full of life.
I absolutely love this rock. One of my favorite aquariums I’ve
owned was filled with this rock, and had a pair of Anemonefishes in it.
Indeed Anemonefishes are not found in the Atlantic waters, and
certainly are not found with the rock, sponges, gorgonian, and other
life that was abundant on my aquascaping. This combination was odd, and
certainly not natural in many ways. But then again sponges, gorgonian,
crabs, Anemonefishes, and algae can be found on reef systems all over
the world. Not only found together, but often relying upon each other
How natural and artificial are water changes? Do the currents
simply bring in vast amounts of clean water and wash away the dirty
water from the reefs? Or is it the same recirculating water moving from
one reef area to the next?
Unfortunately I can’t make this item a two sided debate. Maybe
a reader can help me. So far, all my reading and personal observations
say that growing macroalgae as a way of taking nutrients out of the
water is natural filtration.
To assess filtration methods for natural and artificial
concepts we need to be mindful of the overlapping terms. These two
items are not exclusive but rather very depending on the perception of
the viewer and method being employed. In order to form your own verdict
remember the key question postulated here “In what ways is this
natural, and in what ways is this artificial?”.
Adam Blundell M.S. works in Marine Ecology, and in Pathology
for the University of Utah. He is also Director of The Aquatic
& Terrestrial Research Team, a group which utilizes research
projects to bring together hobbyists and scientists. His vision is to
see this type of collaboration lead to further advancements in aquarium
husbandry. While not in the lab he is the former president of one of
the Nation’s largest hobbyist clubs, the Wasatch Marine Aquarium
Adam has earned a BS in Marine Biology and an MS in the Natural
Resource and Health fields. Adam can be found at email@example.com.
- Blundell, A. (2005a) “Reef Aquarium Filtration Part I:
Mechanical and Biological Filtration”, Advanced Aquarist Online
- Blundell, A., (2005b) “Reef Aquarium Filtration Part II:
Recycling and Removing”, Advanced Aquarist Online Magazine, http://www.advancedaquarist.com/2005/6/lines/,