Fish tank water surface levels ?

The film on the surface of your water is related to not enough surface water movement/agitation. Gases need to escape and unless you have a wet/dry filter, it usually escapes from the surface. Bubblers do a good job of removing these gasses, and so do plants if the tank is set up correctly. Your hang on can also work, but your water level needs to be lower that the output level. Water level is a personal preference as well as safety. You don't want the water touching light fixtures or overflowing the tank. One solution is to have a canopy type lid so it hangs over your tank and you can't see the water level. If you are a DIY, you may be able to make one. Did I answer your question? Hope this helps.

Cheers

The water can not touch the light because the agitation you get from the filter may bounce some of the water into the electrical features of the light. That will either, short out the light or electrify the water.

The noise and ripple should not change from dropping the water level unless you have the pump intake valve too high. Pump intake must be below the water level.

Film on the surface is more complicated. Take a sample of water from the top to the fish store. If a regular water exchange does not work to eliminate the film, it could be something that was in the tank, plants or gravel when you set it up. You can try a one time cheese cloth dip (lower a linen towel into the tank at the edge and spread it out under the water level. Lift slowly from the 4 corners to filter the film up and out. If the film is still there, set up a second tank with it's own NEW filter --in case whatever is making the film is in the filter ) and once the new tank is balanced chemically and temperature the same as your tank, temporarily move the fish to the new tank. Rinse the gravel in the old tank til the water runs clear. Rinse and wipe the inside of the glass with mild soap like dish soap. Rinse the tank completely so no soap residue remains. If the film recurs later be sure to check the nitrogen compounds in the tank. Are there plants? Sunlight allowing algae? Filter not working and the film is from fish waste? Water is treated by chemicals in a water softener? --the sample to the fish store should have uncovered if that is a problem.