Cleaning s/h water jerry cans

[Midnitemo]

Slightly off topic but same train of thought, I am getting an Ibc to catch the rain water of the roof of my new workshop , have been offered various types with different specifications, i fancy black as opposed to clear/white, my thinking is to stop uv causing algae in the long term,is this a sound theory or will increased summer heat up create other problems? Also used ones that have had mustard paste in,yes or no?