iridescent film on betta tank

Question
Ihave a 2 1/2 gal tank with heater and filter. I have a Betta  and keep his tank clean. Feed him small amount each day and take any droppings out each day. I treat new water with Aqueon Betta Bowl Plus and small amount of Aquarium salt.  I have noticed an iridescent film on top of the water. Want to know what it might be and is it dangerous to him   He seems okay-active- no visual sickness. His tank is acrylic and the heater lies at the bottom of the tank.Don't know what other info you may need.  Rebecca

Answer
Hi Rebecca

You did not indicate what type of filter you have, but that film occurs in smaller tanks when the filter is not strong enough to circulate the water and agitate the surface. To my knowledge, the film is harmless to fish. The best way to eliminate the problem is to get a 5 gallon tank with a hang on back power filter. The return flow from these filters will agitate the surface and prevent that film from forming. (The film itself is a combination of bacteria, salt, food and fish waste and other particles in the water)

You could also try another water conditioner such as AquaSafe which is what I use.

Hope this helps, good luck!

Richard