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How does biofilm appear in our fish tanks?

Biofilm appears as a slimy coating to our inner fish tank walls, airline tubing, bubble wands and other equipment, it settles on gravel, ornaments inside and out and with poor surface agitation, can settle onto the surface of the water.

With poor maintenance or poor/restricted filtration, biofilm will build up and as it grows a certain volume, can become free flowing from the attached surfaces. Free flowing biofilm in chunks can cause problems to filters. It has potential to clog filter mechanisms and as a result, restrict the flow which restricts the performance of the filtration. Eventually, this can lead to a cycle bump or complete loss of cycle.

So what is Biofilm?

From what I have learned with my online researching and in the book of Noga, biofilm is an aggregation of microorganisms growing on all surfaces exposed to water or other fluids. These first microorganism colonists stick to the surfaces initially during the weak Van Der Waals forces*. If the colonists are not immediately separated from the surface, they can anchor themselves to the surfaces or existing colonists. Once they have begun colonizing, the biofilm grows through a combination of cell division and recruitment.

One can typically find biofilm on solid surfaces submerged or exposed to liquid of many kinds. Many kinds of bacteria and archaea which are living within a matrix of excreted polymeric compounds can exist in biofilm. This matrix protects the cells within it and facilitates communication among them through chemical and physical signs.

Through nature, biofilm is common as bacteria commonly have mechanisms by which they can adhere to surfaces and each other. If not removed regularly, they can anchor themselves more permanently using cell adhesion molecules such as pili.

Some biofilm have been found to contain water channels that help distribute nutrients and signalling molecules. This matrix is strong enough that in some cases, biofilm can become fossilized.

As an example in other living creatures, particularly humans. Biofilm can be seen on the teeth of humans and presents as a yellowing film over white teeth. The yellowing film is the biofilm. If teeth aren’t brushed free from biofilm, then bacteria will be formed. Once bacteria is formed and the biofilm is still left unattended, corrosion of the tooth/teeth begins. This can lead to cavities and other dental issues. Most know this formation as dental plaque.

Taken from an online source available to the public:

“Biofilm forms when bacteria adhere to surfaces in aqueous environments and begin to excrete a slimy, glue-like substance that can anchor them to all kinds of material – such as metals, plastics, soil particles, medical implant materials, and tissue. A biofilm can be formed by a single bacterial species, but more often biofilm consist of many species of bacteria, as well as fungi, algae, protozoa, debris and corrosion products. Essentially, biofilm may form on any surface exposed to bacteria and some amount of water. Once anchored to a surface, biofilm microorganisms carry out a variety of detrimental or beneficial reactions (by human standards), depending on the surrounding environmental conditions.”

How can we reduce biofilm within our fish tanks?

Regular cleaning of internal walls. Wiping them down with a clean cotton cloth and rinsing that cloth away from the tank in dechlorinated water prior to re-entering into the tank again for the next wipe is a good way. Ensuring you are regularly scrubbing ornaments inside and out including their flat underside surface. Thoroughly cleaning gravel. Using a competent filter which consists of filter media such as bio-ceramic rings, bio-balls, filtration sponges or filter floss etc. The filter’s housing inner and outer as well as its components also requires regular cleaning.

*Wikipedia: The van der Waals equation is an equation of state for a fluid composed of particles that have a non-zero volume and a pairwise attractive inter-particle force (such as the van der Waals force.) It was derived by Johannes Diderik van der Waals in 1873, who received the Nobel Prize in 1910 for "his work on the equation of state for gases and liquids". The equation is based on a modification of the ideal gas law and approximates the behaviour of real fluids, taking into account the nonzero size of molecules and the attraction between them.

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