did you rinse/ wash everything before you set the tank up?
The tank should be washed out with water. You can use a non perfumed soap if you like but just use a cheap non fragranced soap. Use a soap/ chemical free sponge (rinse sponge and wash well with non perfumed soap before its first use to remove any dyes) and then lather up then wash the inside and outside of the tank. Rinse off really well with fresh water.
Put about 2 inches of gravel into a clean fish only bucket and hose with tap water to stir it up. Tip the dirty water out and repeat 6-10 times to remove anything on the gravel. Do this for all the gravel going into the tank.
Wash the filter and filter materials out with fresh water. If you have carbon (black granulated stuff in a mesh bag) for the filter, wash that well before putting it in the filter.
If you don't want to wash everything down use a clean container and put the edge just under the surface of the water and let the water skim over the edge of the container to try and remove the film. It may or may not fix the problem.
