What is the white film on top of water in my betta fish bowl?

The white film on top of your betta's water is likely a combination of a few things:

* Surface film: This is a thin, oily layer that forms naturally on the surface of water. It's mostly composed of organic matter, including dead skin cells, food particles, and bacteria. It can be reduced by using a dechlorinator and by changing the water regularly.

* Mineral build-up: Hard water can leave a white film on the surface, which is calcium carbonate. This is not harmful to your betta, but it can make the water cloudy. You can use a water conditioner to reduce the mineral content in your water.

* Algae: Some types of algae can grow on the surface of the water, forming a white film. This is usually a sign of too much light or nutrients in the water. You can reduce algae growth by using a dimmer light or a water conditioner that removes excess nutrients.

It's important to note that a thin layer of surface film is normal and not harmful to your betta. However, if the film is thick or persistent, it's a sign that your tank needs to be cleaned more regularly.

Here are some things you can do to reduce the white film on your betta's water:

* Change the water regularly. Aim for a 25% water change every week, or more often if the film is particularly thick.

* Use a dechlorinator. This will remove harmful chemicals from your tap water, which can contribute to the film.

* Use a water conditioner. This will help to reduce mineral buildup and algae growth.

* Make sure your tank is properly lit. Too much light can encourage algae growth.

* Don't overfeed your betta. Excess food can contribute to the film.

If you're concerned about the white film on your betta's water, it's always best to consult with a veterinarian or an experienced fish keeper. They can help you identify the cause and recommend the best course of action.