Nitrate keeps high

Ok should have said more info, but I was trying to put something up quick b4 work. It's a 75G w/ 20G sump, 110 lbs live rock, 2" sand bed, 3" LR rubble in sump. . I have a Protine skimmer, phosphate reactor, skimmer filter. I just changed out all my filters that have active carbon in them((4 total)(2 in sump/2in filter)). I have zero phosphate in my tank the reactor is running well. My skimmer is getting about an inch every day so it's running wet. Last week I changed 30 gallons of water and it did a number on the nitrates, then they came back up.
I work so much so I can't get to a LFS to get some macro algae, I think that may be the key to my problem. Every level is dead on, phosphate-0, ammonia-0, nitrite-0, calcium-450, pH-8.2.
Now I noticed since I only have one power head I have lots of junk sitting around my tank. I try to move it around the best I can. Once a week I take it and spray down the rocks and sand and it releases a ton of stuff. I have a wave maker coming in UPS as we speak so I hope that helps wit the junk sitting around.

 

That junk sitting around may well be the source of your nitrate
as may any junk thats accumulated in the rock rubble in the sump
the 10 gallon water change, is much like my previous example
you have a total of around 95 gallons, so a 10 gallon water change, just over 10% means nitrates would have only reduced from 25 - 22.5 and you would not notice that on majority of hobbyist test kits

what may be worth considering is

once you have increased the water movement
this should keep the detritus in suspension until much of it reaches your overflow
in the mean time, when you do your water changes, use the power head to shift this sediment about and at same time add a filter sock, at the end of you overflow pipe, to capture this sediment before it gets to the live rock rubble in your sump
this would be a good temporary and possibly often used maintenance weapon you could add to your arsenal (NB some people run them permenent with weekly cleansing and changing as mechanical filters to remove these particulates before they compromise any sump bio balls or rubble etc)

Steve