okay so i really did it I had no idea that there was too much flow but as I found out there is. today i bought the biggest most powerful pump Rio makes

its the 30hf and for my 90 gallon its too much but that is okay because ive toned it down with a 1 inch ball valve after the water outlet. my overflow cannot keep up at full flow, and even with the aid of my old pump pushing water into the sump it still cannot keep up my hang on overflow is noisy as all heck too how can i quiet things down?? is this amount of flow healthy for my tank? my sand is also moving around because of the amount of flow. any thoughts?