They are more human than most people give them credit. That Koi is a real beauty and can live for decades and so can the goldie there.
Koi are like little water puppies, they love affection and fish do recognize their keepers.
I had a fish buddy and he had a large Pleco that honestly, loved watching TV, especially wrestling. He proved this by blocking his view with large pieces of wood and the pleco would toss that wood and he'd sit at the corner watching.
Ive seen peoples fish harass humans by spitting water across a room and hit with amazing accuracy and they remember those that obnoxiously tap on the tank.
They look happy and healthy and being so healthy they will out grow that home. Build an indoor pond
They are really great.
Oh as far as the film, its been a while but, they used to sell these great magnetic glass cleaners.
I had a large one and it worked GREAT. Part of it was on the outside with a magnet and the other part was on the inside with a scotch brite type of surface. The magnet was strong and you could slide that across the glass , kinda fun.
Check your water and make sure everything is all right. Could be that you need more surface agitation/oxygen and certain bacteria are growing on the glass, just be careful, if the film is not black, brown or smelly, its probably a huge surface of beneficial bacteria doing "good"
I used to leave it on the back and sides and only clean the front. Its unsightly to us but actually a good thing.