Why are pet water fountains such a pain to clean?

What people tried

Every workaround mentioned in the threads below. We haven’t tested any of them — and nobody here is claiming they worked.

1. 1
   Switching back to a standard water bowl or gravity waterer.
2. 2
   Buying filterless fountains that can be wiped out with a sponge once a week.
3. 3
   Scrubbing the fountain completely every other day.
4. 4
   Scrubbing the pump and running clean water through it
5. 5
   Using a baby bottle sanitizer tablet followed by rinsing and drying
6. 6
   Consulting the manufacturer's manual
7. 7
   Replacing the water every other day
8. 8
   Cleaning with citric acid
9. 9
   Switching back to standard water bowls
10. 10
    Throwing stainless steel parts in the dishwasher weekly
11. 11
    Switching to different fountain brands like Pawspik

In their words

Unedited, most upvoted first, each linked to the thread it came from.