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Oil film on to of tank

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Hi guys i have a thick layer of oil film floating above my tank. Not sure what is causing it. Every couple of days i remove it with a paper towel but it eventually builds back up. I suspect its from a specific food im giving. Here is my list of foods.

Sl snowflake

Ada bee food

Bacter ae

Mk cheeseburger

Bacter and snowflake are my prime suspects.

Here are pics. First pic is the oil film. You can see the rainbow.


Second pic is removed oil with paper towel. There are still bits left behind.


I cannot increase water agitation because the tank is so small it will splash around and get the lights and table wet. Its also in my bedroom so will be noisy too.

Have any of you experienced this issue with the foods? Is it bad for shrimp, will they suffocate?

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There are many speculations at the causes, whether it be food, substrate, abundance of proteins, etc. I have had the surface film come and go without any problems. I know when I added floating plants it has helped diminish the culprit. This is just my experience, hope it helps.


I notice the film more often in newer setups, rather than established aquariums.

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The tanks do have 2 HOB filters and 2 spray bars. They just ripple the water but dont produce bubbles. Which isnt enough agitation.

This setup is only 18 cm high and made of 3 chained 8 gallon tanks which is further divided by acrylic dividers. I would consider a skimmer but then i would need many of them for each divided section.

The thing is i have the same problem with my 44 gallon, and that one has a lily pipe above water level with lots of water agitation. However, the oil film remains thick. I never had this issue with that open top tank until 2 months ago when i started putting royal blue shrimp in there and feeding them. Thats why my suspect is the food or bacter. For that setup i could get a skimmer. But im really curious what is causing the oil.

Btw the 44 gal is a 2 year old tank. The small 18 cm tall one is only 3 months old. I would blame the substrate, but it doesnt explain why its happening to both old and new tanks.

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Yea just use a sponge filter and when you do connect and airstone under the connection of,the uplift tube. Attach airline and you have filtration and aeration. It'll stop the film from building. It shouldn't splash around and if that doesn't work consider making a top for it. It's much easier to have one anyways less headache

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Oil film is inevitable. It is just a matter of producing more or less. If the oil film gets too thick, the root causes are generally two:

  1. The food you are feeding contain too much protein or fat.
  2. Your bacteria in the water are dying too quickly.

What is the smell of your water, substrate and filter media? For the smell of the substrate, you can dig up a little (slightly above the top layer) and smell it.


The cheapest and most effective method is running air-pump+air-stone. However, the bubble will splash water everywhere. To counter this, usually put the air-stone at a corner. Use a piece of plastic (can be cut from plastic file cover), fold it into L-shape and stick it to the tank such that it formed a suspended cover over the air-stone.


Alternatively, you can by those self-powered protein skimmer. I know Ehiem and ADA have it.

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