Unless you've worked at a tropical fish shop, (as I did from my late teens to my early twenties), you have no idea what a dirty job it is. It goes way beyond scraping algae.
My first duty each day was to do "a run", which is happytalk for "get a net and a baggie and scoop up any dead fish you find." Nothing like a baggie with smelly dead fish at the bottom to start your day.
The live food smelled worse. We kept tubs of brine shrimp, redworms and blackworms in a fridge behind the scenes. The redworms were harvested from sewage and smelled of it. The blackworms had a rusty, blood like odor. We sold worms by the ounce, so I had to scoop them into little bags with a NyQuil cup. At least the leaches that lived amongst the blackworms never attacked me.
A freezer stood near the fridge. It held frozen sea life from kelp to krill, plus cubes of beef heart and spinach. T.V. dinners for fish. It also served as a morgue for expensive fish. The official word was that they were being "preserved for an autopsy", but the truth was the owners didn't want to part with a fish that cost as much as a television, even if it didn't move. One night the freezer konked out. By the time we reopened the contents were a melted, decaying soup of slop that I had to clean up. After I cleaned it the owners decided to throw it away instead of fixing it. Thanks, guys.
The most horrifying thing was a dead sea anemone. They didn't roll over and die as fish did. They slowly dissolved into a fowl smelling, viscous globs of slime, which rose from them like glop from a lava lamp. It was like an alien bio weapon. If you scooped it out with a net, the goo would ooze through it. Siphon it out and the more meaty parts would clog the tubing. And the smell! It was a foul, evil scent that stayed with your hands the rest of the day, no matter how often you washed.
The job also involved roaches, meal worms, rats and the occasional crayfish, but I think I've made the point on how nasty it could be. Not that I regret it. It makes me appreciate my current job. Any time I feel stressed or overwhelmed I look back to my tropical fish days and I feel much better.