Biofilm (or Surface scum) is a collection of microorganisms surrounded by the slime they secrete, attached to an inert or living substrate in our aquariums. Actually, this is a pretty common thing in our hobby and I do not think that there is a single aquarist who has never had it in the tank. It can happen during the nitrogen cycling process or even in matured tanks.
Fortunately, it is not difficult to deal with biofilm, especially if you are keeping dwarf shrimp. Biofilm is one of the favorite foods for shrimp and it plays an important part in their menu. However, if you are a fish keeper or maybe an aquascaper than it will be necessary not only to remove the biofilm from the surface of the aquarium but also to find the cause of its appearance.
In this article, I will cover everything about Biofilm in our tanks – starting from what biofilm is, what causes it in aquariums and how to remove or ‘create’ it in our tanks.
What is the Biofilm?
At first glance, it may look like oil, it almost has that kind of weird pattern to it. But it is not.
Biofilm is a huge and complex collection of prokaryotes (bacteria) and eukaryotes (such as diatoms, fungi, algae and other multi-cellular and single-celled organisms that form a layer on any surface submerged in water.
Although biofilms include and consist of a multitude of microorganisms, they only take up about 10-40% of the biofilm composition. The other 50-90% is made up of polysaccharides (from the Greek word σάκχαρον (sákkharon), meaning “sugar”) which serve for the storage of energy for those microorganisms and also act as a type of glue. The glue let’s biofilm to attach to any surface in the tanks (such as water surface, driftwood, plants, decorations, leaves, etc.).
What Causes Biofilm in Aquarium
To make a long story short, dissolved organic carbon (DOC) is the cause of biofilm in our tanks. So, what is it?
Dissolved organic carbon is usually defined as organic matter that is able to pass through a filter media. This is a source of energy to support biofilm (a multitude of microorganisms) development and reproduction. This form of organic can be derived from many sources, for example:
- Any type of food we use to feed our pets.
- Animal waste. Pet food which turns into fish (snail, frogs, crabs, whatever) waste still contains a lot of organic matter.
- Leaching substrate. Soiled based substrates have a lot of nutrients that can be used in the process of forming biofilms.
- Breakdown of plant material. This is another great source of organic matter in our tanks.
- Bacteria will gladly decompose the wood and gradually turn it into nutrients (biofilm) that are reintroduced to the food web. If not careful, it is possible to turn your water into a biofilm soup.
What is Dangerous about Biofilm in Aquarium
Biofilms are relatively harmless. However, if you do let it go for a long time then it can definitely cause some damage.
Biofilms can become a problem for aquariums primarily because they consume the oxygen that would otherwise diffuse into the water. It can be especially important for surface biofilm.
By positioning that way (on the surface), those microorganisms (biofilm) will have the advantage of practically unlimited oxygen supply as well as access to the nutrients in the water that they need to grow.
Basically, in an unbalanced tank, it will cause a rapid increase of CO2, which will lead to an asphyxiation of the fish, shrimp, etc. In the worst-case scenario, (want can be even worse!?) excess of biofilm can also suffocate the nitrifying bacteria and completely crash the tank.
Another negative aspect of biofilm is that it:
- promotes bacterial contamination of the aquarium.
- reduces the amount of light for the plants.
- may cause overheating of the aquarium, in some cases.
What is Good about Biofilm in Aquarium
Biofilm is not something unnatural, on the contrary, it is a part of natural processes and also shows you how good your tank is balanced. So, in a well-balanced tank, it can even disappear from a few days to several weeks on its own.
Biofilm microorganisms, which are literally growing on every surface in a healthy and cycled aquarium, consumed by shrimp provide essential nutrients (sterols, essential fatty acids, amino acids, and vitamins) that make them an important food source. It is simply not possible to overestimate the importance of biofilm for shrimp growth.
How to Encourage Biofilm Growth in Shrimp Tanks
Every shrimp keeper knows that a shrimp tank’s success is also defined by how well it can actually grow and maintain its own biofilm. What are the ways of supplementing biofilm?
- Powdered food
Shrimp like biofilm so much that the top food for them (Bacter AE (read more about it here)) is dried biofilm in powder form that promotes, boosts the growth of biofilm in the tank and improves shrimplets survival rate.
- Leaves
In a natural environment, shrimp are surrounded by plants, litter, and leaves. As a part of the natural decaying process, micro-organisms or biofilms will cover all of it. That in its turn will become food for shrimp.
Tip: Let the leaves soak in tank water for several days. When they get a bit murky, it is a sign of developing biofilm.
- Driftwood, Cholla wood, Mopani food, Spider wood, etc.
Wood has a ton of surface area for shrimp to graze on. Although it will take significantly more time for the biofilm to form, it is still a great way to supplement shrimp with it in the long run.
Read more in my article “Driftwood in Shrimp Tank”.
- Blanched vegetables
Blanched vegetables will form biofilm within several hours. It is not advisable to leave blanched vegetables for a long time. They can easily foul the water in the tank.
Read more about “How to Blanch Сucumbers and Zucchini for Shrimp, Snails and Fish the Right Way”.
How Fast Do Biofilms Grow?
There are no hard and fast rules for how long does it take to grow in aquariums. Every tank is different – just like every biofilm is different because of countless numbers and combinations of different microorganisms that make it up. Therefore, it can be from a few hours to several days.
How to Prevent Biofilm
Although biofilms can become a big problem, there is no need to panic because they are easy to handle. So, even if you are a beginner and you have never experienced something like this, it should not be a problem.
- The best way to prevent a biofilm is to maintain a balanced aquarium.
- Overfeeding is your enemy. It is the fastest way to accumulate waste due to uneaten food and increased amounts of waste produced by the fish eating more than they really need.
- Use clean up crew such as snails and shrimp to help you with overfeeding and removing detritus from the tank before it can negatively affect your water quality.
- Do not allow the rotting organic matter to build up. Remove dying or rotting leaves or plants.
- Be careful with driftwood. Do not place too big chunks in a small aquarium.
- Use the lid. Do not let the dust get in the tank.
- Do regular maintenance and water changes. Clean your filters systematically. Biofilm can appear when the flow becomes considerably slower. Take it as a sign that you have to do it.
However, if something went wrong and you see biofilm on the surface of your aquarium, there are also several ways to remove it.
How to Remove Biofilm
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Surface Agitation
A simple airstone (or skimmer) is an easy and effortless answer to this problem. Depending on how bad the situation is and the size of your tank, the biofilm will be completely gone within a few minutes or hours. The cheapest air pump models (check the price on Amazon) can do this job.
The point is that biofilm usually cannot maintain itself even under weak water surface agitation.
Note: If you are using a CO2 system in your planted tank you should know that strong surface agitation will increase the loss of CO2 from the aquarium. At the same time, injecting CO2 without proper surface agitation means that your water may oversaturate with CO2 and gas the livestock. So, keep it in mind and balance the system accordingly.
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Paper towels
Another way to get rid of biofilm requires a clean piece of paper. All you need to do is to just:
– Float a piece of paper over it for a few seconds.
– Lift the paper off and you will notice that all that protein film sticks to it.
– Do the same using another side of the paper.
– Throw away that piece of paper and take another one. Do not reuse it.
Note: Please, do not use the newspaper for this because the ink of paper might get in the water column. There is no need to contaminate it.
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Bottle method
Skim it out with a big plastic bottle or jug. Sink it at an angle and let the surface water with biofilm slowly drain into the bottle. Repeat the process until it is done.
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UV sterilizers
The UV Sterilizers (check out the price on Amazon) use a UV light bulb to eliminate microscopic organisms that are floating freely in the water column. This is a great method of disinfection because they kill most bacteria, viruses, algae, and parasites. These sterilizing units will prevent any biofilm in the tank.
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Hydrogen peroxide
Although I do not like using chemicals unless there is no choice, I still have to list this method as well.
Warning: Avoid direct contact with skin, eyes, and clothing, as well as direct contact with animals or aquatic plants. It is recommended to use protective gear (goggles, gloves). Use it at your own risk!
Sometimes aquarists use Hydrogen peroxide (3%) in spray bottles to eliminate biofilm. For the record, Hydrogen peroxide is commonly used as an oxidizer, bleaching agent and antiseptic. Hydrogen peroxide will simply erase it from the surface.
If hydrogen peroxide gets on the fish, shrimp, snail, etc. or even plants it can harm or even kill them!
Removing Underwater Biofilm
- Use a soft bristle brush (an old toothbrush will be good enough), and rinse in freshwater.
- Snails, shrimp and some fish species like Ottocinclusare your friends. They excellent biofilm and algae eaters.
In Conclusion
In the context of aquarium keeping, Biofilms are a collection of microorganisms. They are always present in our tanks, to some degree. The formation and growth of biofilm may be affected by factors such as temperature, nutrient availability on the substrate, or time.
Of course, biofilms do not look good but they are not that dangerous unless you let them grow uncontrollably and do not take any measures to remove them.