Mixing drum question

[Money pit]

I'm looking for a drum/container to mix my salt water in. I can get a 30gal blue poly drum for cheap. But the only problem is that it had fluorsilicic chloride ( fluoride ) in it. Its been triple washed, but still I think there is probably some left in the pores of the drum that will leach out over time.
Does anyone know what impact fluoride would have on a mixed reef tank ?