The Planted Tank Forum banner
21 - 26 of 26 Posts

· Registered
1,135 Posts

What is it?

Bio-film (biofilm) is a thin film on the surface of aquarium water, caused by the build up of protein from organic waste material. It is the structure bacteria build to support themselves growing on the surface where they get access to oxygen and the material.

What does it look like?

It can be spotted by looking at the surface at an angle to a light source and you may see reflected an oil like rainbow effect. It can also be directly seen by breaking up the surface of the water with a finger or stick to make bubbles. If bubbles form and last for more than a few seconds then you've got a bio-film.

Is it dangerous?

In certain circumstances (high bioload) it can reduce the level of oxygen to the rest of the tank. It can also stop CO2 getting released from the water so CO2 levels rise and so may cause asphyxiation to the animals in the tank including the nitrifying bacteria in a filter.


It can be caused in a new aquarium where the gravel release their organic debris and it settles on the surface.
It can be caused by a male Betta, Paradise or Gourami fish when he constructs his bubble nest. He uses his own mucus to form the bubbles.
Tiny uneaten food particles or decaying plant may rise and gather at the surface.
Add too much bottled bacteria may cause this.
Unfiltered tanks or tanks with very little surface movement are more prone to this than well filtered tanks.

Removing it

Ensure an adequate water flow at the surface or provide aeration to break up the water surface. It will soon dissipate. In the immediate instance a fishnet can be used to take the film off the surface of the water.

· Registered
44 Posts
What is the ambient temp in your room? I'm betting you don't even need the heater. Let the water with the plants cycle. And after a month or two it will be working like a charm.
If it's been up for three weeks it's probly ok to add shimp/snails. Just use a strip test to be sure.
If you see the betta starts acting wierd (laying on the bottom, losing color, etc) you can put him in a small bowl and change the water once a week. This will work as a quarantine tank.

Sent from my iPhone using Tapatalk
21 - 26 of 26 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.