Tips For Clearing Surface Scum/Film On The Top Of Your Fish Tank

Did you peer on top of your planted tank, then discover some terrible stuff or film floating that looked worse than an oil spill from a shipwreck at sea?. This nuisance layer does not look right. It might threaten your aquarium populations.

Most aquarium keepers typically refer to it as surface scum/film or biofilm. It is a cluster of various microorganisms encircled by the slime they produce. It is generally found adhering to the inert or living substrate in a fish tank.

Surface scum is a slightly unusual thing in this hobby, and almost all fish tank hobbyists have it in their aquariums. The reason for this is that it can occur in a new tank setup, where the nitrogen cycling process is still not complete, or even in a mature tank.

Today, we are going to teach you about this mysterious film. Starting from what surface scum is, what causes it, its types of scum, its benefits and adverse effects, and how to prevent and get rid of it from our tank.

What Is Surface Film/Scum On Top Of a Fish Tank?

Surface scum/film is usually found on top of a fish tank, as its name suggests. It is also known as ‘biofilm.’ It is a massive and complex collection of bacteria (prokaryotes) and eukaryotes (other organisms, such as algae, diatoms, fungi, and various single-celled and multicelled creatures) that establishes a layer on any submerged water surface.

When you see it for the first time, it may seem like gasoline on a wet surface, an oily layer that shimmers with a rainbow of colors under the lights. In another case, it may appear to have a white or gray tint and is quite hard to see, forming clumps that then turn into flakes when touched.

Depending on the causes, biofilms can show different appearances in one case than in another.

An interesting fact is that surface scum is composed of a diverse range of microorganisms. They only take up around ten to forty percent of the surface film composition. And the remains, about 50-90% are formed of polysaccharides (from the Greek word σάκχαρον (sákkharon), which means ‘sugar’), which provide energy reserves for the microorganisms and act as a glue for those attaching to any surface objects in the aquarium, such as leaves, decorations, hardscape, water surface, etc.

There are no rules on how long it takes to grow in tanks. Every aquarium is different, just like every surface scum, because of its population numbers and combinations of various microorganisms that compose it. So, it can form over several hours to a couple of days on top of an aquarium.

Common Causes Of Biofilm On Top Of A Fish Tank

As written above, if bacteria and other related microorganisms create the surface film on top of a fish tank, the question is how they can exist in the aquarium.

The answer is ‘Dissolved Organic Carbon (DOC)’; it is the leading cause of biofilm in our planted aquarium.

So what is that? Simply, it is an organic matter that can pass through the filter media. Dissolved organic carbon acts as an energy source to support surface scum in its establishment and reproduction. It can be earned from numerous sources. The surface film can also be stimulated for other reasons, as the following below:

Organic Waste

Decaying plant materials, animal feces, and dead fish are the primary causes of biofilm. In a younger aquarium where the biologicals have not matured yet, or in some tanks with weak/undersized filters. It is frequently slowly absorbed by the filter, making it build up at the water surface. It contains a perfect oxygen level for supporting the microbial colonies growing and feeding on this waste. When it accumulates in your tank, it will stimulate the growth of surface scum and other plagues, as detritus worms and staghorn algae thrive.

Leftover Food

Any food type contains protein and fats. When you add it to your tank, it will dissolve and release materials, as we mentioned before, and float to the surface.

This becomes a particularly serious issue when you feed too much, or some fish choose not to consume it, causing the leftover food to accumulate and release more fats and proteins.

It might be worse if your fish’s food prefers a highly protein-rich diet or contains more oil in those food products.

Leaching Substrate

In some cases, using a soiled-based product for the substrate can lead to the oily film rising. Soil contains a rich nutrient that helps in the process of forming a biofilm.

Wood

Be careful when selecting driftwood types for hardscape decoration. Bacteria can easily decompose and slowly convert it into nutrients (biofilm). In a high case, they can turn your tank water become biofilm soup.

Change In Plant Growth Parameter

Introducing new equipment, light levels, or fertilizers, etc., causes the plants to reprogram their cells to adapt to the new aquarium conditions.

They will release some proteins into the water and then gather at the surface, usually as an oily layer.

Filter And Pump

A new filter can trigger a considerable oil slick because the pump and filter may have a small amount of oil on the moving parts, which aims to lubricate them. Aside from that, other oils that remained during the manufacturing process.

In an old tank with a poor circulation system and gaseous exchange, microbes commonly settle at the surface, where it’s oxygen-rich.

Excessive Iron

There is another type of surface scum that appears whitish, thinner, and breaks easily when touched. This is caused by an iron bacterium (eisenbacteria) because the iron content in the water has exceeded.

Constant Flux

An aquarium with high growth speed and high lighting, accompanied by routine weekly trimming/replanting tasks, will usually be in a state of constant flux and may have a surface film. Although it does not have issues and is mature.

Oil From Your Hand

You may not notice if pores in your hand skin naturally release an oil. It secretes a small amount and does not include oil from lotion or other moisturizer products you used.

When you engage in activities that require direct contact with water, such as trimming plants. During the process, the oil soaks into the water and forms an oil slick on the surface of the fish tank.

Poor Planted Aquarium Location

You may not realize this factor: placing selection can also be a problem, as an oily layer may appear.

A fine mist from perfumes or aerosol has to settle somewhere. It’s possible to locate it in your fish tank, then create an oil coating on the water surface.

Likewise, if you position your aquarium near your kitchen, airborne grease from cooking can fall onto the water’s surface, creating oil slicks.

Types Of Surface Scum Biofilm On Top Of A Fish Tank

Literally, it consists of various microorganisms. However, it can be divided into two different types depending on the conditions present, making the scum appear more specific to a particular organism, thereby forming it. In this case, a particular organism may be predominant, such as a specific bacterium or cyanobacterium (also known as blue-green algae).

Bacteria

A bacterial surface scum typically presents in a silvery-white appearance. Then, if you touch them, they split immediately into smaller parts.

In another case, an oily-looking film is also considered part of ‘surface scum.’ This form consists of fats and protein, so when you pierce your finger with it, it will close up again shortly. The bacteria that live on this scum type feed on the two previously mentioned substances.

Algae

These scum types can also be identified by their characteristics, which are similar to those of algae, commonly characterized by a greenish or blueish color. Moreover, you can see some clusters of foam or even giant bubbles with green or blue edges, indicating they are algae. Foams and bubbles are formed due to hindered gaseous exchange at the water surface.

What Is The Surface Scum Or Biofilm On Top Of A Tank Harmful For Fish And Plants?

The biofilms are relatively innocuous, but if they remain for a long time, they can have adverse effects on the critter populations in the planted tank.

A reason why the surface scums can lead to an issue is that they can absorb the oxygen that should otherwise diffuse into the water, which means they can affect the vital gaseous exchange.

With its strategic position (on the surface), the microorganisms on the biofilm will get many benefits, such as accessing the unlimited oxygen in the air and consuming nutrients in the water, which they need to develop.

It will cause the O2 and macronutrient levels to decrease significantly throughout the tank. Even in aquascape tanks with many plants, they only produce oxygen during the light window, which is typically about seven to eight hours for most aquariums. But the fish, shrimps, bacteria, and other creatures consume it throughout the day.

This makes it clearer that an aquarium is largely dependent on gaseous exchange at the surface for oxygen. You should know that good oxygen levels are essential to help active bacterial colonies break down organic waste and keep algae at bay.

Other bad effects of excessive biofilm on the top of a fish tank include:

• The plants only receive a small amount of light than they require.
• Raising bacterial contamination in the aquarium.
• It may cause asphyxiation to fish, shrimp, and other organisms.
• In some cases, it can increase the temperature, potentially leading to overheating in freshwater aquariums.

What Is Surface Scum Or Biofilm On The Top Of The Fish Tank Offer Benefits?

You must understand if surface scum is part of the natural process, indicating how well your aquarium is balanced.

In a well-stabilized aquascape, it will typically disappear within a couple of days or even a few weeks on its own.

Microorganisms that live in surface films, which are present on every top side of a healthy and cycled planted tank, provide many essential nutrients, such as amino acids, sterols, vitamins, and essential fatty acids, making them a significant additional dietary source. The omnivorous fish like guppies and mollies will love to munch on it.

Most shrimp hobbyists grow and keep biofilm to increase the success chance of their shrimp tank in several ways, as follows:

• Leaf litter: It is a component that’s important for shrimp. Add some dried cattapa leaf, alder cones, etc., and let them soak in the tank. During the decomposition process, microorganisms and biofilm will start to arise, then turn into food for them.
• Wood: regardless of its function as decorations, driftwood (spider wood, cholla wood, mopani wood, etc.) can also release biofilm for shrimp, although it requires more time for it to form. However, it is still a better way to supplement them in the long term.
• Blanched vegetables: creating a biofilm with this ingredient is slightly rapid. It will form in several hours, but do not leave it too long. It probably pollutes the aquarium water. You can use it as food for suckermouth catfish, bulldog, and pitbull pleco love to eat it.
• Powdered food: Bacter AE is a dried biofilm in powder form. This product is rich in nutrients that help promote and encourage biofilm growth, enhancing shrimp fry survival rates.

How To Prevent Surface Scum Or Biofilm On Top Of A Fish Tank

Not only is biofilm detrimental to aquarium populations, but it is also visually unappealing. It can detract from the aesthetic appeal of your fish tank.

Do not panic, it is relatively easier to control than other aquarium troubles, such as algae. Although you are a newbie and have no experience, it’s no problem. Following several tips below, you can keep away surface scum for a long time:

• Maintaining your living aquarium in a balanced condition is the best way to avoid biofilm.
• Keep in mind that overfeeding can be a disaster, so ensure you avoid this bad habit and give your pets the amount of food they need.
• Consider using a clean-up crew, such as a ramshorn snail or garra rufa, to help overcome the overfeeding problem and remove detritus from your aquarium before it affects water quality.
• Do not let the organic matter decompose and gather. Trimming the dying leaves with aquascape scissors and sucking up the rotting plants with a gravel cleaner.
• Be aware of selecting driftwood types. Ensure it’s suitable for aquarium use and fits the tank size, and avoid overestimating the dimensions.
• Using a tank lid is suggested. It can block dust, airborne grease, and dirt into the aquarium.
• Perform a routine water change and maintenance, clean all equipment, mainly the filter parts. An aquarium with slowly flowing water is prone to surface scum.
• Recommended using high-quality soil such as Flourite Black Sand for the substrate.
• Ensure your hand is clean and free from oil. Wash your hands with soap before handling tank water directly, if necessary.

How To Get Rid Of Surface Scum/Film On Top Of Your Fish Tank

There are several methods you can try to eradicate biofilms in your aquarium. Let’s read the guide below:

Surface Agitation

Installing an airstone or skimmer is a simple and effortless trick to resolve this issue. It has probably occurred within several minutes or even hours, depending on the outbreak levels and aquarium size.

Biofilm can not sustain itself in this situation, even under weak water surface agitation. If you are keeping a planted tank, you should be aware that a high surface agitation rate can significantly reduce the CO2 content. Therefore, balancing the system is key to success in this manner.

A safe method is to use a skimmer. It is also compatible with freshwater and saltwater tanks. There are two types of this tool, internal skimmer and external skimmer. Select the one that best suits your aquarium.

Note: Surface agitation using an airstone does not work for marine or coral aquariums

Paper Towel

You just need a clean piece of tissue paper to eliminate the surface film in this technique. Just follow these steps below:

• Drop a piece of paper towel and let it float on the surface for a few seconds.
• Elevate it; you will see that all the oil slick is sticking to this paper.
• It is optional, and you can use the other side of this paper to complete the same task or use an alternative paper.
• After that, discard it, then grab another one and never reuse it again. Repeat this series of processes once the biofilm has disappeared.

Bottle Method

Fill a large plastic bottle or jug, then sink it in a corner and let the oil layer and a little water on the surface gradually enter the bottle. Continue the process until it is completely eliminated from the aquarium.

UV Sterilizers

Eradicating any biofilm using UV sterilizers is more powerful and efficient. An ultraviolet light bulb can kill various microscopic organisms that float freely in the water. This is an excellent disinfection method because it can kill parasites, viruses, bacteria, and even algae.

Hydrogen Peroxide

If you have found a stubborn surface scum and tried all the above methods, but it still hasn’t gone away, the last option is to use a chemical.

It poses a significant risk to your population and can cause your tank to break entirely. If you are a beginner, it is best to avoid this method.

Occasionally, an aquarist is forced to use this way. The first step is to fill a spray bottle with a 3% hydrogen peroxide solution and then spray it directly onto the surface scum on top of the aquarium. Be cautious and avoid giving too many doses.

If it comes into contact with pets (such as fish, snails, or shrimp) or plants, it can harm or even kill them.

Note: Hydrogen peroxide is generally used as an antiseptic, oxidizer, and bleaching agent.

Eliminating Submerged Surface Film

The first method is to clean it with a toothbrush, followed by rinsing it in fresh water. Next, the second option is to keep some tropical aquarium snails, such as zebra nerite. They are an ideal species for eating algae and underwater biofilm.