No water changes after the dosing, because Marine SAT is just bacterial cultures that compete with the algae for nutrients (phosphate and nitrate). So it's not a chemical.
I've been using it for about a year (probably) and noticed a huge difference in water quality and algae levels. I've heard some people say that your tank can become "addicted" to it, and higher and higher doses of it will be required to maintain water quality, but in my tank, I have not found that to be true.
It's very easy to dose, for a tank my size I dump 1/4 gallon in at a time.