That’s a bit of a can of worms to open on here.
It’s been discussed before and many vocal ones would say it’s all placebo anyway so don’t bother.
I personally use it though and I prefer it to without.
I think the recommended dose of vision additives is around 2-3mill per 100 litres. I use a different version so my dose is different, but I think 2-3mill is optimal for the vision mix.
You’ve also got to make sure it’s well mixed throughout the water. I’d put your dose in the empty barrel first, then fill up with pure.