I would say that you need to find a reliable way to turn nitrates into nitrogen(i.e. cheato, mangroves ect.) and i think a skimmer would be bennificial too. For now i would throw something small and hearty in there and observe its actions.
+1
nitrates are the end of the aerobic bacteria cycle. There are a few common ways to remove the nitrates from a tank:
Macro Algae: Algae uses nitrates and phosphates as food in photosythisis. Cheatomorpha being the most used because of its ability to consume nitrates and phosphates relatively quickly without the danger of going sexual and nuking your tank when it doesn't get enough nutrients or light like Caulerpa. If you dont have a refugium type sump this option becomes slightly less viable unless you want to keep the macro algae in your display
Deep sand beds (4" or deeper): either in your display or sump will allow anaerobic bacteria to grow that will slowly reduce nitrites and nitrates into nitrogen gas that will bubble out into the atmosphere. This is where vodka dosing can come in as the carbon from the vodka will feed and encourage the anaerobic bacteria to grow. However unless you really read up about it and know what your are doing I would recommend against it cause a mistake could easily nuke your tank.
Nitrate Reactor: Does basically the same job as the deep sand bed but in a separate reactor that has such a slow flow that it creates an oxygen starved environment for the anaerobic bacteria to live and normally some carbon based media that they feed off.
Algae Scrubber: This uses the same idea of the macro algae but with the micro algae that is already naturally in your tank but giving it a separate ideal environment to live. I don't have any personal experiance with these but I have read some good things about them. Here is an article about them
http://www.algaescrubber.net/forums/viewtopic.php?f=2&t=1432
Water changes: This is the obvious one...as long as your source water is clean this will do the trick. Keep in mind that you are diluting the nitrates with every water change. So if you are looking to lower nitrates significantly you need to do larger % of water changed and several days in a row.