What types of plastics are not reefsafe?

I think you would be taking a risk, it doesn't specifically say "food
grade", shame though,

well, neither does a Rubbermaid garbage can or storage tote, does not mean you
are risking anything though .
For them to place a "food grade" or FDA approval for drinking water storage on
this thing would probably double or triple the cost of the thing
My guess is this thing is made from polyethethylene and is just dandy for water
storage.
There are actually very few consumer plastics that are not "reefsafe" in the
temps/stresses we use.

HTH,
James