My nitrate reading straight out of the tap is 40 to 50

.I feed about 4 to 6 large market prawns daily and a few pellets and algae wafers for my flagtails.I never really feed more than my fish will eat within 5 minutes.I'm running a 100 gallon sump with 1 quietone 9000 and 1 quietone 6000(about 4,000 gph).My sump is loaded to the top with ceramic rings and pond matrix.On the side where the pumps put water back in my tank I also have about 8 big bags full of ceramic rings and I also have a huge air pump meant for ponds,it has 12 outlets for air.I have one outlet running in my sump to promote extra healthy bacteria.and 2 outlets running in my tank.The top of my water makes huge waves.My fish are very healthy and active,i'm just hoping that the nitrate will not effect any of my fish.I've always heard that nitrate is not harmful to your fish,I was just wondering if that is true or not.