white film in freshwater hoses

[iotum]

I had to replace the galley faucet because it inadvertently got a good whack and started leaking. When I pulled the hose off of it that comes from the foot pump, I discovered that there was a white film inside the hose. See attached pic.

This was a bit alarming and I found the same film on the other water hose (tank -> pump). I did not find any film inside the tank itself. I drained the tank by pumping out through the faucet hose with the faucet removed and without the restriction of the faucet the flow rate was much higher and some of the film flaked right off.

I replaced the hoses and flushed the entire system with a mild bleach solution and then lots of water, but I'm curious if anyone has seen this before and knows what it is or how to prevent it from coming back. I'm assuming it's some kind of algae or mold or something, but the pure white color threw me off.