Hello I am very new and need your help with my Red Sea 750xxl tank. I just finally filled it and figured out kinda how to fill my sump enough so the water is running to and from tank normally. However now that the tank is on, the return pump flow into the tank itself pushes aside all my sand leaving a huge empty spot. I tried adjusting the flow valve to the tank but slowing that down slows down the flow to the return pump compartment on the sump leaving that empty again. Any ideas what’s causing this or what needs to be done to fix it?! Any help is greatly appreciated please!! Thank you!