how do you store your horse's vitamins?

how do you store your horse's vitamins at your boarding barn?

My horse gets source vitamins...thats not a problem b/c that's a grain. But he used to get vitiain e tablets and they are gel tablets.. in the summer time they would melt and stick to each other. The sorce and the e tablets are stored in the grain feed trunk which is outside in the sun. Oh and in the summer he gets garlic powder(to keep the flys away)...but the powder is sticking together in these big chunks. It makes it hard to give him a spoonful of it to my horse. Since he's at a boarding barn...i can't keep these things in my tack trunk out of the sun. It has to be in the feed trunk for east access.

So how do you store your vitamins.

Thanks

I keep mine in their original bucket (or if it's a bag I will move it to a plastic bin with a nice tight top) and keep it under my kitchen sink. My horses are at home so that's the easiest way for me.

Find a metal container. Mice ate the side out of a plastic supplement pail and ate most of a jug I had.