Well, after all the fuss, and trying different ways, what I ended up doing was putting the lower bracket angled down, flipping the upper bracket around so the adjustment slider was at the water pump end (Which required a little bend), and most importantly, I tightened up the pulley to where the belt was almost to the edge, as you can see. I'm hoping it's tight enough. It spins when I turn the fan, and it feels as taught as the other belt, so I'm guessing it is.
Thanks for help for all those that answered my questions.
Thanks for help for all those that answered my questions.