Well “Biofilm” it’s there all around us .. As well as inside us ...Any damp
dark area it thrives ….. What causes Body order or your mouth to stink or teeth
to decay.. What is the relation between Koi , and bad breath --well bacteria
..
Someone truly said , Just keep
the Bacteria ---the bacterial will keep your Koi ..
Now again let’s turn to our
beloved Koi Guru Mike for what he has to say …
I also have to thank My other Sensais Saiicu ,Yerrag ,Rick and Ray Jordan for the
contribution to Mike's discussion ..
We often talk about beneficial
bacteria and nitrifying bacteria when discussing koi pond filtration systems.
Looking back in the popular literature, there is little or no mention of "biofilm".
About a dozen or so years ago, there was quite a bit of discussion about biofilm on
the old NI board and the term began being used with frequency in koi circles. I
now find that a number of people use the term without having any real idea of
anything more than 'biofilm is
where the good bacteria live'. So, a bit of discussion of biofilm seems
worthwhile.
I often talk about a 'mature pond' when discussing nitrification, greenwater
and other biological aspects of the koi pond. I tend to think of a mature pond
as one that is a year or two old. What I actually mean, however, is a pond with
an established biofilm. Biofilm is
an assemblage of microbes that are associated with one another in a matrix of
polysaccharide material produced by bacteria in the assemblage, attached to a
substrate. It is the 'slime' you can feel on a surface that has been submerged
for a while. It is this polysaccharide matrix that is crucial to appreciation
of biofilm,
because it creates an hospitable environment for the resident microbes and
allows intercellular communication. Just like people get under a roof (or cave,
etc.) to avoid exposure to sun, rain and harsh temperatures, this 'slime'
material allows survival, growth and reproduction in a hostile environment.
In Nature, biofilm is
all around. Virtually all bacteria live in multi-species communities in which
there are mutual interdependencies. We are familiar with some bacteria
converting ammonia to nitrite and others converting nitrite to nitrate. This is
a simple example. The interdependencies are innumerable and complex. It is
enough for us to understand that few bacteria can thrive if truly alone. The
species need other species to supply one need or another. By associating with
one another in the biofilm matrix,
the resident bacteria are much more effectively able to take/share/get what they
need from the others. All have a role to play, a contribution to make. And, in
the process the biofiilm community creates its own micro-system, with an
internal environment that differs from the external, and something of an
internal eco-system. It is far more complex than simply a home for nitrifiers.
There can be hundreds of species of bacteria thriving within a biofilm.
The biofilm can
be multiple layers thick, with the resident species varying between the outer
layer and the deeper layers. Many of the species have evolved together over the
eons to the point where there is a sort of communication among them. Chemical
substances released by one will trigger responses in other species. In many
ways, the matrix of creatures lives as if it was a single organism with the
constituent species playing specialized roles.
Biofilm will
form on just about any substrate. The plaque on your teeth is a type of biofilm.
So, in our ponds every submerged surface is territory forbiofilm formation...
the pond walls, the interior surfaces of pipes, the walls of the filter units
and, of course, the filter media selected because it has great surface area in
a small volume. When we set up a new pond, free floating bacteria are
immediately present, arriving from the air, from any object that was submerged,
from the fish placed in the pond. These bacteria have appendages called
fimbraiae. The fimbraiae give the the little germ the ability to attach to a
surface. They are very effective in attaching as long as the surface is not bactericidal
itself. In short order, micro-colonies develop that are glued in place. These
are not easily removed. Scrubbing will certainly reduce the size of the colony
greatly, but it would have to be a super-human scrubbing to get rid of all the
bacteria. As soon as the micro-colony is established, the bacteria begin
producing EPS... extra-cellular polymeric substances. This material forms a
barrier around the micro-colony. This EPS barrier also becomes a substrate,
with microbes joining it. So, with an infinite number of micro-colonies being
formed by numerous varieties of bacteria, it takes little time before the
surface of a new pond will have a slimy feel to it. But, this biofilm is
immature. Over a period of weeks and months, more species join the matrix. In
time, the beneficial nitrifiers we talk about so much are present, but so are
numerous other species, including ones we would consider harmful. But, all of
them form one biofilm in
a mutually beneficial community.
This slime is not as simple as it at first seems. Over time, multiple layers
form, and there can be different bacterial populations within the layers. Most
of the reproductive activity, however, occurs in the outermost couple of
layers. The lower layers within the biofilm can
go into a reproductive stasis. If something comes along and scrapes off the
outer layers, the bottom layer re-energizes and can recreate the lost layers.
Bacteria also seem able to move between layers to some extent in response to
changes in nutrient availability, environmental conditions and other factors.
At the same time, there is death occurring within the biofilm.
As bacteria die, their corpses supply nutrient to the community as a whole.
With age, the polysaccharides will degrade/decompose producing a calcified
deposit at the base of the biofilm.
This deposit creates an extraordinarily strong attachment to the substrate.
Curiously, this single biofilm develops
structures as if it was itself a single organism. There are tiny 'canals' that
form, which you can think of as being something like pores in human skin. These
canal structures carry water (and its oxygen and minerals) to the lower layers.
Some waste products can even be discharged from the biofilm through
these structures, which form something of a labyrinth within the biofilm.
Just as bacteria join the biofilm as
it develops, bacteria can move out of it. Some scientists believe the biofilm is
capable of expelling redundant bacteria that are not contributing to the
community.
Once a biofilm is
fully established, it becomes very tough to eliminate. They can be setback by
exposure to chemicals, by drying out and physical force, but it is really tough
to eliminate the biofilm altogether.
Even if dried out thoroughly for several weeks, put the dried out biofilm back
in water and it will come back robustly in a comparatively short time. Some
refer to biofilm as
being nearly indestructible because studies have shown that complete removal
requires the equivalent of sandblasting. But, pondkeepers should not put much
weight on such ideas. Bacteria within the biofilm are
also sensitive to environmental changes. The efficiency of nitrification can be
affected by shifts in temperature or pH, by medical treatments and very mild
chlorination. So, there is both fragility and strength in the structure. In a
sense, the structure endures, but our concern is with it functioning
efficiently to maintain the pond water.
And, as a concluding comment, do not get the idea that all biofilm is
the same. It is not. The constituent species will vary according to the
environment in which it exists. In our ponds, there will even be some forms of
algae taking up residence in the biofilm.
So, when we talk about a mature pond, a large part of what is meant is that the biofilm is
mature.... it has developed all of the interacting species suited to the
environment of that pond, in the proportions that function well in that pond,
and have the strong attachment and mutiple layers that come with time. Such a
pond can withstand all the little stresses so much better, because its biofilm can
withstand them and has even adapted to them in the range of species present.
But then does It mean that you need biofilm needs to be brownish
always.. what if your media is not
covered with slush
Yes, a dark color is not
better than a light color. I do not know all the things that can affect the
color of biofilm. I know that in a
pond stained with tannins, the biofilm will be
brownish. Mats I place in the top tray of my Bakki stay light colored except
where algae glarf is captured. That portion of the mat captures fines and will
be stained yellow-brown. In my Nexus filters the moving bed K1 media seems
white until new K1 gets added. Then it is obvious that the older K1 is
yellowish. I have seen K1 that was very dark where used with heavily loaded
tanks in commercial facilities. I think a lot of what we see is often not so
much the biofilm itself
as debris that sticks to the surface of the biofilm. In your
situation, the frequent removal of debris from the system is probably
minimizing the attachment of fines, resulting in the mats being lighter.
It is easy enough
to see that used media is not the bright white of new media, but sometime take
out a piece of K1 (or similar media) and visually examine it closely. There are
so many different shades of color. And, you may even see a speck of green.
...How does a speck of what seems to be algae colonize a piece of K1 that is in
an enclosed container, churning with aeration? It's an amazing world on every
piece of media.
It does seem that I've
been seeing a lot of threads around the 'net lately where pondkeepers have been
dosing chemicals or blasting ponds clean. I guess it is 'Spring cleaning' in
June? They end up with the various symptoms of 'new pond syndrome'...
greenwater they've supposedly never had before, sick fish, cloudy water, etc.,
and they ask what they can use to make everything alright .... make it be like
it was before chemicals and pressure washers were used to decimate the
bio-community of the pond. Of course, they cleaned the pond because it was not
properly designed (maintained) and there was a build-up of gunk on the bottom
(rocks on the bottom/ no bottom drain), or some other frustration. They react
with a burst of energy to make everything pretty, like when the pond was new,
with no appreciation for the fact that problems will recur if you just treat symptoms
and not causes.
It takes work to
maintain a pond, but it is so much easier if you do not work against Nature and
instead let Nature work with you. [And, I'm not talking about bog gardens! 
]
Now when did the bio film
start ??
It began forming as soon
as water was added to your pond with low enough chlorine levels that bacteria
could survive. It is on all the surfaces of the pond, the filter mats, the
pipes ...everything. What you may not have is a fully mature biofilm. That comes in
time. You may recall discussion of how a forest forms? Think about Mt. Helens,
wiped bare by the volcanic eruption back in the 1980s. First there were various
small plants that colonized... mosses, lichens, a few clumps of grass. In time
various shrubs and seedling trees took root. What was barren became green. Over
the years ahead, the trees will grow and eventually there will be a forest. The
accumulation of leaves over decades provides soil for more types of plants and
trees to thrive, and with the expanding variety of plants comes an expanding
variety of animals. A real forest comes into existence. The forest on the rocky
mountainside is not the same as a forest in a river valley nearby, even though
they are one continuous swath of forest. Each area within the forest differs
according to the nutrient available, the type of soils, the exposure to drying
conditions, etc. The main trees will differ as you go up to higher elevations. Biofilm is
similar. There is a progression. It takes time for everything to come together.
Some microbes that 'want' to join thebiofilm cannot
do so until the biofilm has
progressed to a state where its residents are producing the nutrients and
environment needed. The more variable the environment (climate zone, sun-shade,
chemical exposures), the longer it will take to reach a mature state with
multiple layers.
In a sense you can
see the biofilm on
pipes and such in the pond, but you will not really see it without using a
microscope. We speak of biofilm'thickness', but it
is very thin. Just that slimy smooth surface you feel with your finger..
Biofilm is a function of the totality of the pond
environment. If the water is lacking oxygen, the biofilm will
have anerobic bacteria in ascendance. The anaerobic bacteria are 'bad', but
using PP to eliminate them does nothing to address the environmental condition
- oxygen depletion. Disease causing bacteria are likely in residence to some
degree. The proportion will be higher or lower in response to the environment.
If there is a lot of organic waste to rot, the biofilm engaged
in the decomposition will have a high population of organisms ready to attack a
scratch and start an ulcer. Anyone who has torn out an old pond has seen how
slimy the interior of the plumbing can be. And, a lot of gunk can be captured
in the biofilm. The plumbing from
bottom drain to filter system often collects debris that has to be flushed out
regularly to minimize the rot occurring in the pond. The biofilm in
those pipes will undoubtedly have a high proportion of the microbes we would
prefer not be around. But, they are present because of the waste in the lines.
If eliminated by a strong dose of PP, they will return as long as waste is
going through the lines.
I have to disclose
my bias against using chemicals in the pond. And, when the use of a chemical is
necessary (such as treating for parasites), I strongly prefer whatever will do
the job with the least collateral impact. So, I have an especially strong bias
against PP, because it is so very thorough and effective in oxidizing
everything. With that bias disclosed....
IMO, a situation
would have to be extraordinarily extreme to 'bomb' the pond with PP to the
point of destroying the biofilm. Other than
sterilization to eradicate KHV, I cannot think of a circumstance where I think
it would be justified.
I'll use the forest
analogy again. Let's say we want a forest of mixed tropical hardwood trees, but
we get a forest of eucalyptus. We can burn away the eucalyptus over and over,
but we will not get a mixed tropical hardwood forest unless the conditions are
right AND we stop burning everything down so the hardwoods can grow and
reproduce. PP is like using fire to burn away the forest. If instead, rainfall
is increased (and other environmental elements made conducive to tropical
hardwoods), the eucalypts will decline in proportion and either disappear or
have a minor presence. The tropical hardwoods will prevail because the
conditions suit them.
Likewise, the more
we can make the conditions in our ponds suited to our koi, the more the biofilm will be
composed of the microbes suited to those conditions. Our main focus is on the
nitrifiers, although biofilm is
affecting many components of the water. So, we want the water to be highly
oxygenated for the benefit of both our koi and the nitrifiers. We want to avoid
extreme temperatures and fluctuations in pH. We want water parameters best
suited to our koi. Those parameters will also result in a biofilm best
suited to our pond and the needs of our koi. It is all connected.
But doesn’t biofilm buildup also live deposits like Calcium
indie of water tubing..
"Deposits in the
form of biofilm and biofilm with
entrapped debris are generally easy to comprehend, but biofilms may often lead
to the formation of mineral scales as well. Calcium ions are fixed into the biofilm by the
attraction of carboxylate functional groups on the polysaccharides. In fact,
divalent cations, such as calcium and magnesium, are integral in the formation
of gels in some extracellular polysaccharides. If we can imagine these calcium
ions being fixed in place by the biofilm at the
heat transfer surface, then it would make them more readily available to react
with carbonate or phosphate anions that are present. This would then provide
nucleation or crystal growth sites that would not normally be present on a biofilm free
surface. Additionally, biofilms may entrap precipitated calcium salts and
corrosion by-products from the bulk water that will act as crystal growth sites.
A typical
biofilm-induced mineral deposit that we are all familiar with is the calcium
phosphate scale the dental hygienist removes from our teeth. When biofilms grow
on tooth surfaces, they are referred to as plaques. If these plaques are not
continually removed, they will accumulate calcium salts, mainly calcium
phosphate, and form tartar (scale). One could make a comparison between rinsing
your mouth twice daily with an antiseptic mouthwash to control plaque, with
feeding microbicides and biodispersants to control biofilm related
deposition in heat exchangers. If biofilms in heat exchangers are not
controlled, then, like dental plaques, mineral scale may result."
So, it seems biofilm can
increase the rate of scale formation.
And, in another
study, the article abstract indicates that at high hardness levels the rate of
calcium precipitation increases greatly:
Effect of Calcium
on Moving-Bed Biofilm Reactor
Biofilms
Authors: Goode, C;
Allen, D. G
Source: Water
Environment Research, Volume 83, Number 3, March 2011, pp. 220-232(13)
Abstract:
The effect of
calcium concentration on the biofilm structure,
microbiology, and treatment performance was evaluated in a moving-bed biofilm reactor.
Three experiments were conducted in replicate laboratory-scale reactors to
determine if wastewater calcium is an important variable for the design and
optimization of these reactors. Biofilm structural
properties, such as thickness, oxygen microprofiles, and the composition of
extracellular polymeric substances (EPS) were affected by increasing calcium
concentrations. Above a threshold concentration of calcium between 1 and 50
mg/L, biofilms became thicker and denser, with a shift toward increasingly
proteinaceous EPS at higher calcium concentrations up to 200 mgCa2+/L. At 300
mgCa2+/L, biofilms were found to become primarily composed of inorganic calcium
precipitates. Microbiology was assessed through microscopy, denaturing grade
gel electrophoresis, and enumeration of higher organisms. Higher calcium
concentrations were found to change the bacterial community and promote the
abundant growth of filamentous organisms and various protazoa and metazoan
populations. The chemical oxygen demand removal efficiency was improved for
reactors at calcium concentrations of 50 mg/L and above. Reactor effluents for
the lowest calcium concentration (1 mgCa2+/L) were found to be turbid (>50
NTU), as a result of the detachment of small and poorly settling planktonic
biomass, whereas higher concentrations promoted settling of the suspended
phase. In general, calcium was found to be an important variable causing
significant changes in biofilm structure
and reactor function.
So, yes, those
instances of scale build-up in plumbing lines restricting flow are directly
related to biofilm interacting
with the hardness of the water.
And What about the
effect of sunlight on the media ….??
Direct sunlight does
kill bacteria. The EPS of biofilm provides
some protection. So, yes, filter media should not be exposed to direct
sunlight, and darkness is better still. After all, we do not need algae growing
on and clogging the media...
