I have noticed that my water will leave a slimy pink film on certain surfaces like a sink drain, bath toys, or dog water bowl. What would cause this and how can I fix it?
What you're most likely looking at is a bacteria called Serratia Marcescens.
According to Wikipedia it is
commonly found growing in bathrooms (especially on tile grout, shower corners, toilet water line, and basin) as well as many other places.
From that source (and others), the best way to get rid of it is regular cleaning by soaking & scrubbing with bleach-based disinfectants.
I've also been doing research for a school project (relating to reddish and bluish stains on water fixtures) and some sources had said that the red stains are from copper. In other words i'm assuming copper has entered your water through the pipes and the only way to fix the issue would be to essentially replace the pipes in general. Bluish stains resort from iron as well.