This is my take on this product.
There are several causes for slime algae and it is important to address the ultimate problem. There is no miracle cure, IMO. If you have conditions that are conducive to growth of this algae, you may STILL have conditions conducive to the growth of this algae in the future.
I have used this product. I used it when I could no longer stand to look at my tank, let alone improve it. But it was done after trying all other methods to deal with the algae. Once the tank improved, it was easier to get motivated to care for it.
But be warned, things can go wrong with dosing these sorts of products. I personally wouldn't use it without considering this.
And I would definitely do a water change as recommended.