Back in 2013, I wrote a program which removes moving things from a series of photos. Leaving only the background.
How? By glorious programmer magic!
Well, I experimented with different algorithms for calculation color medians. I did get the best results from an algorithm I call the topological rank algorithm
I tested the program on a series of photos of my sisters aquarium. The image to the left is one of the original photos, and the image on the right is the altered image, with all the fishes removed. You can see an orange remnant of one of the fishes at the lower left corner. This could be easily remedied simply by using more photos. But, who has the energy...
Now to the fun part. Imagine this: You are house-sitting in a house with large aquaria containing lots of expensive fishes. You use my program to create some images of the aquaria emptied of all the fish. Then you mail the images to the owner of the house, saying "Sorry, they died off, one by one. All gone. Apparently booze and fish don't mix.".
Mikael K J Ericsson