I peered over the top of my aquarium only to discover that it looked worse than the aftermath of an oil spill. That thick layer of grime just didn’t look right. And, I realized it might actually be dangerous to my fish!
Today, I am going to teach you where this mysterious oily film comes from and how you can get rid of it.
Recognizing an oil slick in your fish tank
An oily film in an aquarium can take on many forms, depending on the underlying cause. Sometimes, it appears as a clear layer of oil that shimmers with rainbow colors under your lights, resembling gasoline on a wet surface.
In other instances, it might be a gray or white film that is difficult to see through and clumps together when agitated.
This gray or white film is actually a protein buildup, common in tanks that house bettas. But don’t fret, it can be removed in the same way as any other oily film on the surface of your aquarium.
You may come across different names for an oil film such as biofilm, but it doesn’t change the fact that it needs to be removed.
Protein film
A protein film, also known as protein foam or protein scum, is a white, foamy substance that can be found on the surface of the water in fish tanks. It is typically caused by organic waste, such as feces, dead aquatic life, and uneaten food in the tank.
These organic materials lead to the formation of small air bubbles, which can emit an unpleasant odor.
Algae film
A tell-tale sign of an algae film in your fish tank is its color. It is typically a bright green and slimy in appearance. Your tank water may also appear cloudy and green, resembling pea soup.
Algae growth in an aquarium is often caused by an excess of nutrients, typically resulting from poor maintenance and overfeeding, or too much light.
Bacterial film
A white or silvery film on the surface of the water in your tank is often a sign of a bacterial film or biofilm. When touched, it will disintegrate into small segments. This film develops as bacteria consume the excess organic waste present in the water.
This type of oil film is particularly common in planted tanks that are fertilized, as it is typically caused by a buildup of iron in the water.
To combat this, reducing the amount of iron in the water by using a fertilizer with less iron content is a good solution.
Oil slick
An oil slick is a thin layer of oil that can be seen at the surface of the water in your tank. It can take on a rainbow color when light hits it. These slicks are commonly caused by external oils, such as grease or dirt from hands that come into contact with the water.
Why is there oil in my aquarium? Understanding the causes
A small amount of oil is enough to create an unsightly film on the surface of your fish tank.
Sometimes, just a drop or two can cause a problem. But what is the origin of this oil or protein?
Let’s examine 8 common causes of the oily film that can appear on top of your aquarium. In some cases, solving the problem is as easy as identifying the cause.
Oil from your hands
Oil from human hands is a prevalent cause of oil slicks in aquariums. It is common to need to submerge your hands in the water while caring for your tank, such as catching a fish with a net or adjusting plants.
The oil that naturally secretes from your skin’s pores, as well as any lotions or moisturizers you may have applied, can wash off and create an oil slick on the surface of the water.
The solution is simple, you can wash your hands thoroughly before putting them in the aquarium. Make sure to rinse off all traces of soap, as that should not be in the tank.
Another option is to use aquarium safe gloves when working in your tank.
Fish food
You might be surprised to learn that many types of fish food contain fats. When you feed your fish, the food dissolves and the fats and proteins inside float to the surface of the water, creating an oil slick.
This can be a particular problem if you overfeed your fish, as any leftover food will continue to dissolve and release the fats inside.
Although it may be difficult to avoid oily, high-protein fish food, depending on your fish’s diet but don’t worry. Later in this guide, I will show you how to prevent oil slicks from forming in your tank.
Fish poop
It’s an inevitable fact of owning an aquarium, your fish will produce waste and it can be oily.
The waste produced by fish can be oily because of the oily food they consume.
However, it’s not just the food that causes the oil, the fish’s digestive system also produces oils and proteins as it breaks down food.
When the fish release their poop, these oils rise to the surface, forming an oil slick.
Dead fish
The death of a fish is a sad reality of owning an aquarium. If a fish passes away and its body is not removed promptly, it will release fats and oils into the water as it decomposes.
This can not only create an unsightly oil slick, but also lead to a strong and unpleasant odor.
It is important to regularly check your fish population and be aware of any missing members.
Filters and pumps
It may come as a surprise that the new filter you just installed could be the culprit behind the giant oil slick in your aquarium.
Filters and pumps contain small amounts of oil on their moving parts to lubricate them and also some residual oil from the manufacturing process.
To minimize the amount of oil released into your aquarium from the filter, it is recommended to wash the filter thoroughly before using it.
This will help to remove any excess oil that may have accumulated on the filter. It’s a simple step that can prevent the formation of oil slicks in your aquarium and help maintain the overall health and appearance of your tank.
High levels of iron in water
An overabundance of iron in the water can lead to the formation of an oily film caused by bacteria, which is a common issue in planted freshwater aquariums that use fertilizers.
To solve this problem, consider using a fertilizer brand that contains less iron or reducing the amount of fertilizer used in the tank.
It is important to monitor the iron levels in the water and make adjustments as necessary to maintain a healthy and clear aquarium.
Maintaining balanced iron levels is crucial as high levels of iron can damage plants, discolor the water, and encourage the growth of unwanted algae.
Poor fish tank location
Are you confident that none of the other causes on this list are responsible for the oil slick in your aquarium? The oil film on the surface of the water may actually be caused by human activities.
It’s easy to overlook the fact that the fine mist from aerosols and perfumes can settle on the surface of your aquarium and cause an oil film to form.
Similarly, if your fish tank is located near your kitchen, the grease from cooking can settle on the surface of your fish tank and create an oil slick.
This is especially important in open aquariums (without lid).
To avoid this problem, it’s best to place your aquarium as far away as possible from potential sources of contamination such as aerosols, perfumes, and kitchens.
Choosing the right location for your aquarium before setting it up can help prevent issues like this.
Poor water conditions
An overall decline in water quality can lead to the formation of an oil film on the surface of the water.
This is a common issue in both new tanks and mature aquariums that have been neglected for extended periods, also known as “old tank syndrome.”
Regular maintenance such as performing water changes and vacuuming the substrate are essential in keeping your tank clean.
A water change should be done at least once a week, and more frequently if the tank is overcrowded. A gravel cleaner should be used to vacuum the substrate.
Additionally, aquarium equipment and filter media should be cleaned on a regular basis, using the water from the tank, and not tap water.
Is the film harmful to fish?
An oily film covering the surface of your aquarium may not only be unsightly, but it can also be dangerous for your fish.
While a small amount of oil may not harm your fish directly, if it accumulates, it can block the surface of the water and prevent oxygen from entering the aquarium.
Oxygen is essential for the survival of fish, and a thick oily film can act as a barrier, suffocating the fish.
Even a small oil slick can reduce the amount of oxygen that enters the water, and in an overcrowded tank, this can lead to a disaster.
The film not only prevents oxygen from entering the tank but also traps carbon dioxide, which can be harmful to your fish.
Given the risk it poses to your fish, it’s essential to remove the oil slicks from your aquarium as soon as possible.
How do I get rid of oily film in my aquarium?
Why don’t all aquariums have an oily film on the surface? The constant movement of water, especially agitation at the surface, helps to mix and disperse small amounts of oils, which can then be removed through water changes and filter maintenance.
Aquariums without movement are more likely to have oil buildup. However, if you are dealing with a substantial amount of oil on the surface of your aquarium, it’s important to take steps to remove it and prevent it from returning.
Use paper towels
An oily film on the surface of your aquarium can be unsightly and difficult to remove, but don’t worry, there is a simple solution that you probably already have on hand:
Paper towels.
By turning off all equipment that causes water movement and laying a paper towel on the surface for a few moments, the oil will cling to the paper towel, allowing you to easily remove it.
If you have a large tank or a significant amount of oil, you may need to repeat this process multiple times.
For a steady hand, you can also carefully drain the surface scum into a clean container. Once the oil is removed, take steps to prevent it from returning in the future.
Water movement
Water movement is crucial in preventing the buildup of oil on the surface of your aquarium.
By using equipment such as a filter nozzle, powerhead, spray bar or even an airstone to create bubbles, you can mix oils and prevent them from forming a thick layer.
If you notice an oil slick in a specific area of your tank, it may be a sign of poor water circulation.
To fix this, adjust the position of your filter outflow and power heads to ensure that the water is moving throughout the entire tank and preventing the formation of oily patches.
Use a surface skimmer
If you’re tired of dealing with oil slicks on the surface of your aquarium, the Fluval Surface Skimmer may be the solution you’ve been looking for.
This easy-to-use device attaches to the inflow of your aquarium filter and quickly removes floating oil, algae, and other debris.
The skimmer works by having two holes, one at the top, and one at the bottom. The top hole is strategically placed at the surface of the aquarium, allowing water to be drawn in and any floating debris to be filtered out.
While there are electric surface skimmers available, I recommend the ones that attach to the filter inflow. They work just as well, and don’t require additional electricity or take up space on a power strip.
Say goodbye to oil slicks and hello to crystal-clear water with the surface skimmer.
REMEMBER!
It’s important to distinguish between a surface skimmer and a protein skimmer as they serve different purposes. A surface skimmer is designed to remove floating debris and scum from the surface of your aquarium, while a protein skimmer uses bubbles to remove dissolved waste that sinks to the bottom of the tank. Protein skimmers are typically used in saltwater aquariums, while surface skimmers can be used in both freshwater and saltwater setups.
How to prevent the formation of a film or oil layer on top of the tank?
Eliminating greasy films on the surface of the water can be simple, but the ultimate solution is to keep them from forming altogether. Taking preventative measures is the key to maintaining a clean and oil-free tank.
Add surface movement
Keeping your aquarium free from oily films is about more than just removing them, it’s about preventing them from forming in the first place.
One of the best ways to do this is by providing adequate water surface movement which helps to mix oils into the water.
Utilizing a powerful filter or air pump can also help to improve water circulation and prevent stagnant areas in your tank, as well as increase oxygen levels.
Perform regular tank maintenance
An oily water surface can be a sign of poor water conditions and an excess of organic waste in your aquarium.
To prevent this, it’s crucial to maintain a clean tank and equipment, as well as commit to regular water changes to remove excess waste and promote stable water chemistry.
To maintain a clean tank, it’s recommended to perform a water change at least once a week, removing around one-third of the water and replacing it with clean, dechlorinated or distilled water.
Additionally, use a gravel cleaner to vacuum the substrate once a week to remove debris, decaying plants, and feces.
Regularly inspect your aquarium, at least once a day, for dead aquatic life, especially in areas that are difficult to see like the back of the filter or among decorations.
If you have a lot of live plants in your tank, make sure to prune and trim them regularly and try to reduce the amount of fertilizers high in iron.
By taking these steps, you can prevent oil slicks and maintain a healthy and clean aquarium.
Wear gloves
To ensure that your fish are living in a clean and healthy environment, it’s important to keep your hands clean when performing maintenance on their tank.
One way to do this is by wearing gloves when working inside the tank. If gloves are not available, make sure to avoid using any lotions or moisturizers on the day of tank maintenance.
It’s also crucial to wash and rinse your hands thoroughly before performing maintenance. This simple step can prevent dirt and grime from transferring from your hands to the fish tank, keeping the water clean and your fish healthy.
Stop overfeeding fish
An oily water surface can be caused by overfeeding fish, so it’s important to be mindful of how much food you’re giving them.
Provide your fish with only as much food as they can consume within a minute or two, and remove any uneaten food with a net.
To further prevent oily buildup, choose high-quality food brands that are lower in fat for your fish.
In conclusion
An oil film on the surface of your aquarium may not be pretty, but it doesn’t have to be a major problem.
By following the tips and techniques outlined in this guide, you can easily remove the oil slicks and keep your tank looking its best.
Do you have any other methods or tips for removing oil slicks from aquariums? Share them in the comments below!
