The sump and the skimmer have very little effect on turnover. You should rely on your return pump from the sump as well as some well placed powerheads to create your flow and turnover. With the 1000g/h sump pump, you are turning your tank over 13.3x/hr. Not too bad, but the addtition of a couple powerheads would improve things. Plus, powerheads will also add more internal flow to your tank, thus, reducing dead spots and creating a more caotic type current. Look at a couple of Maxi-jet 900s or 1200s. Ideally, you would like your total turnover to be 15-20xtank volume/hr. Good luck...Lando