Mixing drum question

[Money pit]

I used to use a brute garbage can, but I always had about 5 ppm nitrate in my water from it. So I'm looking at options. I like to make up my new water about a week in advance incase of an emergency, but the down side is its a week that stuff can leach out of the container. The one that had fluoride in it is the same drum as the food grade container that I was also quoted $80 for.
Which is what lead me to wondering if it's usable.
Garbage pail is a good idea, if I can find on that isn't plastic. Plastic leaches, Bis phenol A. its estrogenic to us, so I would think it wouldn't be too healthy to the fish or coral. Maybe thats what was causing the nitrates in my old mixing drum, not sure really, just a thought.