Sometimes one fish dies, without any apparent disease. In previous aquariums I would always remove them as fast as I could.
Now my aquarium is a bit bigger, and I have some laziness to remove those bodies: they are to deep, or in the back, or partially eaten. So I decide to leave some, and they tend to disappear in few days.
Is there any safety issues by doing that? Will other fish die if they eat dead fish? Will they develop some mad fish disease ?
Sometimes, after you have a established aquarium, with everything working as it should, fish might die simply because they get old, or have a shorter life-span due to its condition before being sold to you, or because some other fish had a fight with it.
If only one fish died, without white / black spots, no sign of fungus or parasites, no alteration in the gills, I usually rule out diseases of environmental problems.