I see people asking how to store multiple bags of grain securely for their horses all the time. As with everything horse, everyone has an opinion… but this is what I do for my grain storage!
I use a contractor job site box so I can have multiple grain bags and types, without multiple containers, and they stay protected. This way I can feed right out of the grain bag and never have old grain at the bottom I need to worry about using up before I can get new grain (like if Murdoch’s is having a sale and I want to buy grain now!).
The particular model I have can hold 12 bags of grain standing upright. Plus it has sliding cubby shelves to store other items I want protected.
You can find them used, for relatively inexpensive on Craigslist or Facebook Marketplace.