Bought one once--not the same brand as yours, but the same sort of thing. I didn't really think it was what we wanted to use regularly, but at the time I wanted something with iodine in it, something I knew the horses would actually use, and when I went shopping that had the best iodine content of the products available. Our horses weren't using their iodized salt blocks & we had an iodine deficiency.
Anyway, when I put that tub out, those horses never pulled their heads out of it. It didn't matter which pen I put it in, it was the same with all the horses. They just got busy and licked up that molasses. When they did come up for air they had molasses from the tips of their noses to the base of their ears....sticky, sticky goo. I told them they were going to get ants....
#1-they were getting far more molasses than they were iodine from that tub
#2-they didn't need that much molasses
#3-I couldn't have afforded to keep buying tubs at the rate they were devouring that stuff!
So, I continued shopping & came up with the Equest Range Horse blocks--a mineral/salt block made for horses. It's more porous & easier for the horses to lick/chew than ordinary salt blocks, and my horses will use them.
I've since switched to a different block--this one is made by Co-op, but is a similar idea. It's a horse mineral block w/salt, sort of a soft block that is also easy for the horses to chew on & lick--I like the analysis of it better than the Equest (which is saying something, because the Equest was a good product) and it's a little bit cheaper to buy than the Equest. The horses like it just as well if not better than the Equest, so that is what I now buy for everyone. I know my horses are using the blocks & therefore are getting the minerals they require, and there's no sticky, sticky goo, no ants & no high sugar content!