Stupid question about DIY mixing station

[keithw283]

I am building a mixing station and am looking to find used barrels since new ones are incredibly expensive. I found a guy selling 58 gallon food grade barrels for $30 each. They were used to store olives. My stupid question is, would that be harmful in anyway to my aquarium and what would be the best way to clean them?

 

[Peace River]

Here is a thread that may help with your question:

https://www.reef2reef.com/threads/cleaning-food-grade-barrels-for-awc-system-how-to.834673/